Not much is known about Casey Jones, except for the fact that he clearly knows about the existence of mutants. Casey has created his own arsenal of weapons, which he uses against his enemies; mutants and criminals alike. It is hinted that he has been down in the sewers and he might even have his own lair set up down there. In the online comic, Casey had spray painted "Jones is Everywhere" with his iconic ice hockey goaltenders mask tagged next to it, possibly indicating that he goes go down there occasionally.
- "Mutagen Man Unleashed" - In his debut-episode, Casey encounters April in the hallway where he tells her that she's his tutor. Even though he proved he would be difficult to work with, he says he's willing to cooperate if it means staying on the ice hockey team. April agrees to help him and decides to tutor him that night in the park. When they start their session, Casey tells April that he's not interested in trigonometry and wants to be an ice hockey player or a international bounty hunter once he graduates. Despite everything April had witnessed that day, he surprises her by asking who wants to live a normal life. When April sighs a bit, Casey shows empathy. He then notices a smudge on her face and wipes it off, which shocks Donatello, who is watching them from a rooftop. On their way back home, Mutagen Man shows up and tries to approach April. Casey steps in front of her and manages to get a couple of hits in. However, he and April barely fend him off, but they are able to shake him off and escape unharmed. They make their way back to April's apartment while watching out for anymore mutants. They make plans for their next tutoring session just as Mutagen Man prepares to go after April. Casey almost heads towards the alley where the Turtles are fighting Mutagen Man when April redirects him to the other way.
- "Target: April O'Neil" - He meets April in the ice hockey rink where they strike up a conversation. He asks her why she doesn't hang out with other people, which results in her telling him that she and her friends "are fighting". He relates her situation to his friendship with his best friend Nick ending after an accident occurs during an ice hockey game the previous year, resulting in Casey's best friend being hospitalized. Even though April says that he didn't mean to hurt Nick, Casey repeats Donnie's words, saying that it was beyond his control. Just then, when Casey goes to change, the Foot Bots attack April. He shows up and starts fighting them off while telling April to leave him. Despite his wishes, April helps him fight the soldiers and leads a few away. After the Turtles defeat Karai and her robots, April returns to the rink to find Casey unharmed.
- "The Good, The Bad and Casey Jones" - Casey first met Raph when he's fighting 3 members of the Purple Dragons, when Raph tries to stop him from possibly killing them. The next day at school, April wonders what's wrong with him since he got quite a lot of bruises from the fight, which he claim is from practicing hockey. He then was brought to the Turtles' lair and found out about the secret and everything. He later fought a Foot bot with Raph and ended up being friends and joining the team.
- "Fungus Humungous" - Casey is seen at the beginning of the episode, reading a paper while sitting next to April. He hears her say that it's nice to have someone else knowing about the turtles, which is still a secret. He later falls under the spell of the fungi and sees many rats as that is his fear, but in the end, he is cured.
- "Of Rats and Men" -
- "The Manhattan Project, Part 1" -
- "The Manhattan Project, Part 2" -
- "The Lonely Mutation Of Baxter Stockman" -
- "Newtralized!" - Casey and Raph hit a roadblock in their friendship throughout the episode. At one point, Raphael angrily accuses Casey for allowing the Newtralizer to escape. Casey retaliates, stating that he was just trying to help the turtles complete the mission, and that he always has their back. However, Raph doesn't accept this, saying "Oh yeah? When was that?" Visibly hurt by Raphael's words, Casey says he's saved them "dozens of times" before walking away, trying to cool off. Later on, he comes back and helps the turtles fight off the Newtralizer, thus succeeding this time around.
- "The Wrath of Tiger Claw" -
- "Plan 10" - Casey accidentally switches bodies with April while fighting the Kraang along with the turtles. He keeps staring at April's butt while in her body, to which April (in Casey's body) yells at him to stop doing that. Embarrassed, he grins nervously and says, "Oops! My bad." Soon enough, they switch back. Casey is now bummed because he admitted that he actually liked being a girl, especially since it was April's body.
- "A Chinatown Ghost Story" - Donatello, April, & Casey are seen on the rooftop spying on the Purple Dragons. Once again, Donnie and Casey's never-ending rivalry of winning April's affection gets in the way, to which April chastises them for jeopardizing the mission. Later on, Donatello's brothers are mind-controlled by Ho Chan, an evil Chinese spirit from the Shang Dynasty who also successfully attempted to control the Purple Dragons. April and Irma also get kidnapped by Ho Chan. Donnie and Casey reluctantly join forces in order to defeat their enemy and manage to free Leonardo, Raphael, & Michelangelo from Ho Chan's control while saving April (and Irma) from the evil spirit's trap.
- "The Invasion" - Casey Jones and Raphael are looking for Karai on the rooftops. Casey asks Raphael, while looking at some graffiti he did, and if April ever talks about him. Soon, some cops come and try to arrest Casey. He hits them with a Hockey stick revealing them as Kraang Droids. Soon, he and Raph make it to April's house. After Leonardo comes crashing through the window, they hop into the Party Wagon. Casey drops April, Donatello, Michelangelo, and Raphael off at the base, while he looks for his little sister and father. Casey delivers a blow to Kraang Prime by driving the Party wagon into his suit. Then Casey, Raphael, Michelangelo, Donatello, April, and an unconscious Leonardo drive away to the O'Neil farmhouse. Casey sadly confesses to April about how the Kraang probably got to his father and little sister because he couldn't find them anywhere.
- "Within the Woods" - Casey continues training with Raphael, Donatello, Michelangelo, & April at the farmhouse for the next three months while Leonardo is still unconscious from the events of previous episode. The next day, after Leo finally wakes up and the two older brothers continue their training in the woods, Raphael gets kidnapped by the Creep. Leo orders his remaining brothers, April, & Casey to split up and search for Raph in the forest. Leonardo tells April & Casey to team up, which angers Donatello, though it satisfies Casey. However, the two humans also wind up kidnapped by the Creep while trying to save Raphael. Donatello and Michelangelo soon join them to fight off the creature, followed by Leonardo, who ends up saving all of them. Casey waits with the others at the barn, where Donatello successfully cures Raphael.
- "A Foot Too Big" - Casey doesn't have much of a role in this episode, but he does interact with Leonardo at the barn, talking about Donatello's "new girlfriend" who happens to be Bigfoot. After witnessing her running into the woods crying, Michelangelo angrily calls them out for it, to which Casey looks at them guiltily and apologizes, stating that he didn't mean to hurt Bigfoot's feelings. It is still unknown whether or not Casey finds out about the kiss between April and Donnie at the end of this episode.
- "Buried Secrets" - After locating a hidden Kraang ship in the basement, Casey is surprised to find out that the inhabitant is April's mom. When April's mother wonders about Kirby's whereabouts, Casey is about to tell her what really happened to him, to which Raphael punches his arm, stating that he had to "pull a Mikey" in front of her. Later on, Casey and the older three turtles berate Mikey for attacking April's mom with his nunchucks. Angry and upset that his brothers and friends don't believe him, Michelangelo storms out of the barn and hangs out in the kitchen with Ice Cream Kitty, leaving Casey and the others looking at each other in confusion. Before Raph confronts him and April about the Mom-Thing, he expresses sympathy for April wanting to leave her friends behind at the farmhouse and go with her mother.
- "The Croaking" - Casey helps the Turtles and April search for Michelangelo in the woods. However, the Punk Frogs misinterpret Mikey's words about how badly his brothers and friends treated him earlier, thus kidnapping April, including himself. Despite this, Casey eventually helps the frogs escape, by knocking out the leader Attila and carrying him to safety. Casey is with April as Attila wakes up and she tells him not all humans are evil as they watch their home burn to the ground. He's then pleased to see Attila has changed his views of humans and expressed his gratitude for saving him. He is relieved to see that Michelangelo's okay and welcomes him back (along with the others).
- "In Dreams" - Overall, Casey helps April save the Turtles from their nightmares involving the Dream Beavers, who are originally from the Dream Dimension. At first, the two plan on buying groceries from a nearby store, asking the Turtles if they want anything. Michelangelo wants spicy gummy worms, but April says that the store only sells general needs, to which Casey agrees. Once they reach the store, they find out that the owner (Bernie) owns a mysterious book that happens to be linked to the Turtles' dreams as well as the Dream Beavers. Later on, Casey demands Bernie to help him save the Turtles before they end up dying in the real world.
- "Race with the Demon" - While driving back home with a bunch of groceries, Donatello and Casey are at each others' throats again, which causes April to scold them and be quiet for the remainder of the ride. After returning to the farmhouse, he demands to go after that road maniac, despite April's protests. The next day, the pair calls each other names in alphabetical older while working on the Turtle Racer. Both of them decide to give it a test run, but Casey intends on going after the maniac driver alone, thus ditching the others, much to Donnie's dismay. Casey defends his actions, claiming that the police aren't around to handle it, so he has to instead. Still disappointed that he wasn't allowed to help, Donnie continues working in silence, causing Casey to feel guilty and apologize for ditching him earlier. Donatello hesitantly agrees to help him fix the Turtle Racer and defeat the maniac driver (revealed to be a car mutant named Speed Demon) together. Unfortunately, it attacks Donnie and literally swallows him, transforming into a half-Speed Demon, half-Donatello super-mutant. The mutant then challenges Casey to a race: whoever wins gets to determine Donnie's fate. In the end, Speed Demon is successfully defeated as Donnie and Casey happily accept their newfound friendship, giving each other a permanent "peace hug", much to Raph and April's slight dismay.
- "Eyes of the Chimera" - Casey is seen sparring with Leonardo and Raphael. Feeling bad for Leo, Casey tells Raph to go easy on his brother, since Leo is still recovering from his leg injury. After being kidnapped by the Chimera, Casey, Raphael, Donatello, & Michelangelo struggle to escape the creature's nest, which happens to be a geyser that's about to erupt.
- "Vision Quest" - While the turtles are spiritually refining themselves in the woods for three days straight, Casey remains behind and continues sparring with April. She manages to defeat him several times and slightly gloats about it. Once Casey spots the turtles in their spiritual gear, he stares at them in awe.
- "Return to New York" - Casey drives the Party Wagon back to New York.
- "Serpent Hunt" - Casey stays behind at Antonio's Pizza-Rama with April and Master Splinter, though he's disappointed with the turtles because they refuse to let him help.
- "The Pig and The Rhino" - Casey teams up with Raphael while searching for Karai. Later on, he's seen helping April and Donatello on Coney Island.
- "Casey Jones VS. The Underworld" - Frustrated that he wasn't involved in the fight against the Kraang, he decided to take on the Purple Dragons on his own. Unfortunately, he stumbles upon their new leader (Hun), thus losing the fight (even though he stopped the Purple Dragons from getting the cash). Back at the lair, the Turtles make fun of him for losing to the Purple Dragons, which infuriates him before storming off and encountering Don Vizioso, a famous mafia boss who runs gangs in New York. To Casey's surprise, Shredder demands Vizioso to supply him with dangerous chemicals from Auman Chemicals, the largest chemical plant in the city (according to Donatello). Disguising himself as a waiter, he eavesdrops on their conversation, but gets caught by the Shredder himself, threatening Casey to go away or else he'll kill him. Feeling genuinely afraid, Casey nods his head and runs away, filled with adrenaline before texting Raphael about the whole situation.
- "Meet Mondo Gecko" - Feeling bored, Casey asks Michelangelo if he wants to hang out with him. While skateboarding on the building rooftops, they encounter a new mutant named Jason (a.k.a. Mondo Gecko), who was mutated into an anthropomorphic gecko due to the mutagen spill that occurred in "The Mutation Situation". Feeling bad for Mondo's fate, Mikey decides to get to know him and soon become good friends. However, Casey is skeptical of Mondo's true intentions and tries talking Mikey out of it, but to no avail. After defeating the Purple Dragons, he berates Mondo for stealing the money they stole, causing an argument between the two. Mikey attempts to resolve their issue, though his attempts are unsuccessful. However, Casey is proven right when Mikey gets captured by Mr. X, who happens to be Fishface. Casey calls him out for it while they're trapped in an underground cell within the sewers, but Mikey rolls his eyes in annoyance, tired of being treated like an idiot. Soon enough, Mondo apologizes for betraying them and joins the two as they race against Fishface and luckily win.
- "The Deadly Venom" - While encountering Karai for the first time in person, she kisses Casey on the lips, thus poisoning him before he passes out, dying (though luckily Donatello saves him in time, along with the others).
- "Attack of the Mega Shredder!" - Casey aids Raphael, Donatello, & April while attempting to locate Leonardo & Michelangelo, since they ran away despite Splinter ordering them to remain in the lair until Raph's foot heals properly. Donatello suggests using the Turtle Mech (which Leonardo disapproved of during "The Invasion, Part 1").
- "Annihilation Earth! Part 1" - Upon learning of the impending invasions by both the Kraang and the Triceratons, Casey joins April and the Turtles with attacking the Technodrome, and then the Heart of Darkness when it is deployed in Washington Square to be used on the Earth.
- "Annihilation Earth! Part 2" - Casey is captured with the Mutanimals when they attempt to shut down the Heart of Darkness, only to be rescued later, but is unable to stop the Black Hole Generator from being activated when Shredder murders Splinter. Luckily for Casey, he, April, and the Turtles escape Earth's destruction thanks to the Fugitoid. Casey appears to be excited while heading out to explore the universe.
- "Beyond The Known Universe" - As the Fugitoid turns back time six months to allow the Turtles, April, and Casey a chance to prevent Earth's demise a second time with finding and destroying the Heart of Darkness, they set course for another part of space. When the Ulixes (Fugitoid's spaceship) is damaged by asteroids, as the gang suit up in spacesuits, Casey finds one that is equipped with high-tech photon hockey pucks for him to use in place of his homemade ones. After landing on the planet Varanon so the Ulixes can be refueled and repaired, Casey and Raph make the mistake of accidentally decapitating the robot merchant of a weapons store, causing the security robots to chase after them to pay for the damages, before fleeing when the gang run into Lord Vringath Dregg, who takes Casey prisoner for disrespecting him and prepares to eat him before the Turtles and April intervene, destroying Dregg's latest purchase by accident, further angering him so he sicks his Vreen on them, then overpowers them personally, forcing them to flee back to the Ulixes and escape. Dregg gives pursuit, and manages to get one of his Vreen aboard, but Casey kills it with a photon puck. However, though they escape Dregg, they end up face-to-face with the Triceraton Armada.
- "The Moons of Thalos 3" - An encounter with a Salamandrian fighter that had been engaging the Triceraton Armada leads to both it and the Ulixes crashing on an icy moon, where if the Fugitoid can not find the material he needs to fix the Ulixes before the life support in everyone's suits run out, they could all perish on the moon. After running into the Salamandrians who were in the fighter that crashed with them, the Turtles and the Salamandrians soon form an uneasy alliance to get the material the Fugitoid was looking for back to the Ulixes, with Casey sacrificing his photon pucks to stop a herd of Ice Dragons from pursuing them, but once back at the Ulixes, their life support finally runs out. However, the Fugitoid is able to repair the ship and get everyone inside just in time, saving Casey and all their lives. Casey and the Turtles depart on better terms with Y’Gythgba and G’Throkka, hoping to see them again in the future.
- "The Weird World of Wyrm" - Arriving at the ruins of an abandoned spaceship, as they explore the inside of the ship, Casey humorously makes a wish to battle some zombies. Unknown to him, the ship was home to the hyper-cube prison of a genie-like creature called Wyrm. When Casey finds the cube, Wyrm grants his wish and revives the dead crewmen as zombies to fight Casey and the others. They manage to escape back to the Ulixes with Wyrm's prison, and despite orders not to touch it, Casey does, and releases Wyrm. After, Donnie makes a second wish, for Casey not to be such a big dummy, which makes Casey become super-smart, then the Turtles make the mistake of making a third wish, thus freeing Wyrm, who beings to take over the Ulixes. Worse, Casey, with his newfound knowledge, sides with Wyrm to take down the others. However, before he kills them, Casey asks for one more wish. Wyrm, seeing no threat, grants it, only for Casey to turn the tables on him and use the wish to undo everything that's happened up to before Casey made his original wish. When he's about to make it again, April stops him, having a feeling he had better not say anything. With that, everyone returns to the Ulixes, leaving Wyrm trapped in his prison, pleading for them to make a wish to let him out in futility.
- "The Outlaw Armaggon!" - Casey and the others are attacked by a bounty hunter hired by Lord Dregg by the name of Armaggon, forcing them to hide in a space station where they unintentionally awaken the dormant A.I. of the station, Overlord. Armaggon has Overlord crank out an army of VX3 Warbots to capture Casey and the others, but when Overlord reveals his true intentions of eliminating organics for machines, Casey is nearly turned into a robotic drone before Armaggon intervenes, under orders from Dregg to bring them back alive. After April frees the Fugitoid from Overlord's control and he causes the station to self-destruct, Casey and the others escape back to the Ulixes, and resume their pursuit of the Triceraton Armada, not realizing Armaggon is still after them for his bounty.
- "Riddle of The Ancient Aeons" - Traveling to the planet that is home to the Aeons, Xaava-Dal, Casey is among those affected by the dark atmosphere of the planet as it increases his anger and hostility towards the turtles, especially Donatello. Thanks to April and the Fugitoid, he is able to overcome the atmosphere's influence on him, and help to restore the Aeons' Sol Star that, in turn, restores the planet and the Aeons themselves to normal. After meeting the Aeons in their true form and being thanked for helping them, Casey and the others depart to pursue the Triceratons, who got away with the first piece of the Heart of Darkness.
- "Journey to the Center of Mikey's Mind" - Casey doesn't have a major role in this episode, but once the Neutrinos invade Michelangelo's mind, he tells Fugitoid that Mikey is pretty much mindless in general. Luckily, Michelangelo is already unconscious at that point. Once all the turtles regain consciousness, he reveals to Mikey that it wasn't a dream.
- "The Arena of Carnage" - Having caught up to the Triceraton Mother Ship, Casey remains on the Ulixes with the Fugitoid and April while the Turtles infiltrate the Mother Ship to find the first piece of the Heart of Darkness. However, the Turtles are captured, forcing Casey, April, and the Fugitoid to infiltrate the Mother Ship instead. While the Fugitoid is captured and taken before Emperor Zanmoran, he buys Casey and April time to find the main armory and retrieve the first piece, only to soon be fired upon by the returning guards. As they flee, they crash into the Turtles and Fugitoid, who had taken Zanmoran prisoner, knocking off the Emperor's crown. As the Tricertons who had been following April and Casey hold their fire upon realizing the Emperor was in the crossfire, it gives Casey and the others time to escape through an airlock, retreat back to the Ulixes with the first piece, and escaping before they can be pursued by Raptors.
- "The War for Dimension X" - Casey is forced to remain behind on the Ulixes with April while the Turtles and Fugitoid travel to Dimension X to speak to the Utrom Council about helping them find the remaining two pieces of the Heart of Darkness. Casey doesn't take it too well as he bangs his hockey stick against the floor in frustration.
- "The Cosmic Ocean" - Traveling to the home of the second piece and its guardians, the Daagons, it is not long before Casey and the others meet the Daagon leader, Hiidrala, and learn that in order to get the second piece, they need to prove themselves worthy to the Cthugga. However, the Ulixes is attacked by Armaggon, and after he commandeers it, they are soon forced to flee from the Cthugga. After Armaggon is apprehended by the Daagons, Casey and the others return to Hiidrala to be told they failed and won't get the piece. However, Lord Dregg and his Vreen arrive, and a battle ensues. After Leo protects Hiidrala from a missile from Dregg, she summons the Cthugga to devour Dregg and Armaggon. Casey watches in surprise as the Vreen, having lost their hive mind in Dregg, stop fighting and flee. With Casey and the others having proven themselves to Hiidrala, she entrusts the second piece of the Heart of Darkness to them, hoping they can destroy the infernal device, and declares them heroes of the Daagons. With two pieces in their possession, Casey and the team head after the final piece.
- "Revenge of the Triceratons" - Before they can reach the location of the final piece of the Black Hole Generator, Casey and the others are ambushed by the Triceraton Armada. After Casey jokes about Mozar being demoted back to Captain from Admiral for losing the first piece of the Black Hole Generator, Mozar attacks the Ulixes. After having a Rock Rocket loaded with the Skeevix Virus impact the Ulixes and decapitate the Fugitoid, Casey pokes the Rock Rocket with his hockey stick, releasing the Skeevix larvae to scamper off an find somewhere to cocoon and evolve into their true forms. Casey is forced to deal with them alongside April and Mikey, and are able to slay all the evolved Skeevix, but they are unable to overpower a trio of Raptor pilots when they board the Ulixes to retrieve the first two fragments from them. Thanks to Donnie repairing the Fugitoid, they are able to take out one, but the other two escape with the fragments. Despite the setback, Casey remains encouraged to find the last piece before the Triceratons do.
- "The Evil of Dregg" - Responding to a call for help from Y’Gythgba regarding G’Throkka being taken by Dregg and Armaggon to Sectoid 1, Casey and the gang travel there to rescue him, but Casey disturbs a hive of Xaxx Bees, and unintentionally smacks one into Donnie's face, causing Donnie to suffer repeated alien bee stings, and have to be taken back to the Ulixes for medical treatment by April and the Fugitoid. Despite that, Casey and the others fall into Dregg's trap, as Mona and Sal Commander betrayed them to protect their own home world. Though Casey frees them from the cage they were in while being guarded by Armaggon, Dregg knocks them into a pit to face the Scorpinoid. They manage to escape, thanks to April causing a distraction, and joined by a vengeful Sal Commander and Mona when they learn that Dregg has no intention of calling off his invasion of their home world, they are able to overpower Dregg, Armaggon, the Vreen, and the Scorpinoid, and escape Sectoid 1.
- "The Ever-Burning Fire" - Traveling to Magdomar, where the final piece of the Heart of Darkness is located, Casey ends up having to deal with Lord Dregg again when he chases them down, looking for payback for the Scorpinoid. Later, when Chompy Picasso gives away their position to the Triceratons, they are forced to fight them for a short bit before escaping. When the guardian of the final fragment, Tokka, awakens, Casey and April are tasked with protecting Chompy, only to discover that Chompy is Tokka's baby, and return him to her with no problems. However, when the Turtles free the final fragment from Tokka's shell, Dregg gains hold of it and delivers it to the Triceratons, who then detonate the nearby dwarf star to allow their escape, with Casey and the others barely escaping themselves. Later, Mozar contacts them to reveal his intent to use the Heart of Darkness on Earth, to the horror of Casey and the others.
- "Earth's Last Stand" - As the Ulixes returns to Earth, Casey is happy to be able to see his family again, but upon learning that the Fugitoid is the one who built the Heart of Darkness, he is furious that the Fugitoid deceived them. After Leo attempts a useless one-man assault on the Triceraton flagship that nearly costs him his life while the Ulixes nearly crash-lands on Mars, they return to Earth, only for the Fugitoid to dump them out of the Ulixes when they refuse to cooperate with his latest plan. Meeting up with his past self, they are able to disarm the Heart of Darkness and overpower Mozar, forcing him to retreat to use the Devastator on New York City before retrieving the Heart of Darkness to wipe out the Earth. However, the Fugitoid sacrifices himself to see to the destruction of not just his doomsday weapon, but the Triceraton flagship as well, leaving Casey to figure out what to do with two of him on Earth. Thankfully, the past Fugitoid arrives to take the past Turtles, April, and Casey into space, allowing the future Turtles, April, and Casey to return home with Master Splinter, the Mutanimals, and their other allies.
- "City at War" - Casey attends the ceremony of April's promotion to full Kunoichi by Splinter, and joins in the celebration with the Turtles following Splinter completing the ceremony.
- "The Insecta Trifecta" - With the knowledge that Shredder is still out there and a threat to New York City, Casey teams up with Raphael to patrol one sector of the city, only to soon respond to the alarm of a nearby bank that has been broken into that the NYPD sends a cruiser to investigate as well. The perpetrators of the robbery are Stockman and his two new henchmen, Antrax and Scumbug. While Casey is ready to throw down with them, he is forced to go it alone due to Raphael suffering another of his panic attacks from his bug phobia and running off in terror, leaving Casey to be overpowered and captured. Taken back to Stockman's lair, Casey taunts Scumbug before he is gagged while Stockman decides to move their lair elsewhere when Scumbug worries the Turtles will come looking for Casey and find them. As a result, Casey is taken to Stockman's new lair in a skyscraper construction site after he has kidnapped April, Leo, and Karai as well. Before Casey can be used as food for Stockman's henchmen, Donnie, Mikey, and Raph arrive to save them, but once free of the web he was stuck in, Casey is unable to help much due to being scared of heights, but in the end, Stockman flees back to Shredder in defeat while the Turtles capture Antrax and Scumbug, along with retrieving the stolen money as well.
- "Bat in the Belfry" - Casey is out on his bicycle, bored with not seeing some action, when he notices several civilians running for their lives. Investigating the situation, he finds himself face-to-face with Monoculus, a monster from Mikey's comic book. Sending a picture to the Turtles, he soon has their help, but all of them are overpowered except for April, who easily destroys Monoculus with her Tessen fan and her Aeon crystal. While April, Leo, Raphael, and Donnie return to the lair, Mikey stays with Casey to consider how Monoculus came into reality and think that April's Aeon crystal is behind it. When Mikey returns with it and tries to use it to bring Wingnut and Screwloose to life, Casey mocks his efforts and gets into a fight with Mikey, before both are blown back by an energy burst from the Aeon crystal that does just as Mikey hoped and brings Wingnut and Screwloose to life. After mistaking Casey for being an accomplice to Mikey, Wingnut and Screwloose allow Casey to join them and Mikey with protecting the city from crime, but when Mikey and Casey spill the beans about Wingnut and Screwloose's history, then show them the Aeon crystal that was responsible for their revival, entranced by the crystal, Wingnut and Screwloose take it, only to be transformed into more animalistic forms and flee with the crystal. Casey and Mikey tail them to a clock tower, and are soon joined by the rest of the team in the Turtle Blimp. Thanks to April hitting the church bell and thus weakening Wingnut and Screwloose, Casey is able to help keep them incapacitated long enough for April to retrieve her crystal and revert them to normal. Afterwards, Wingnut and Screwloose accept that they have to go back to their comic book world, and Casey sees them off as April returns them to their comic book, before comforting Mikey as he cries over how he enjoyed the time he spent with them and how he may never get that chance again.
- "The Super Shredder" -
- "Darkest Plight" - Casey and Raph continue facing off against Shredder's henchmen after sending Donnie and Mikey down in order to locate Splinter, who has recently fallen into the abyss.
- "The Power Inside Her" - Casey joins Leonardo, Raphael, and Michelangelo while they plan on stopping Za-Naron from taking over April's mind completely. On the other hand, Donatello (who remained in the lair with Splinter in order to keep a close eye on April) decides to convince April to snap out of it on his own. This fails, however, resulting in April literally disintegrating Donnie, allowing Za-Naron to have full control over her mind and body (despite Donnie's pleas). Visibly horrified due to witnessing his best friend's death, Casey still believes that April isn't completely gone, so he begs her to remember who she is once Za-Naron brutally attacks Raph, putting himself in harm's way to try and get April to regain control of herself.
- "Tokka vs The World" - In the lair, Donnie and Casey reveal their concern about April's well-being after the events that took place in the previous episode. Later on, Casey and Mikey team up to prevent Tokka from destroying Earth in order to take her son (Chompy) back home. Unfortunately, they get kidnapped and threaten to dissect Michelangelo, assuming that he's also an alien threat.
- "Tale of Tiger Claw" - When Tiger Claw's sister (Alopex) accidentally scratches Casey's cheek with her blade, April reveals that he's officially cursed. Casey doesn't believe this at first, despite encountering other supernatural beings in the past. Finally, he gives in and begs Alopex to help him be free of this curse.
- "Requiem" - Splinter tells the Turtles, April, Casey, & the Mutanimals to split up (though Dr. Rockwell and Mondo Gecko aren't present in this episode). Casey joins Splinter, Raphael, April, and Slash and helps them fight Shredder on the rooftop. Meanwhile, Leonardo leads Donatello, Michelangelo, & Leatherhead towards Coney Island in order to defeat Be-Bop and Rocksteady. However, both teams fail miserably. To make matters even worse, Shredder stabs Splinter and throws him off the roof, thus killing him instantly. Out of grief-filled rage, Casey manages to crush Shredder while he's stuck in a garbage truck, hoping to finish him off once and for all. He walks behind Donnie and sadly watches him openly cry over Splinter's body. April and Raph soon reach them as Casey hugs April close to him, trying to comfort her. Unfortunately, at the end of the episode, Shredder is revealed to still be alive.
- "Owari" - He, April, and the Turtles journey to Shredder's lair to finish him once and for all, but are separated from the Turtles by the Super Shredder throwing down Molotov Cocktails to cut Casey and April off from Leo and the others. However, Raphael, Mikey, and Donnie are soon knocked off the roof, leaving Leo to face Super Shredder alone, who he succeeds at slaying once and for all, presenting the mutated Kuro Kabuto to Casey and the others to signify Shredder's demise.
- "Scroll of the Demodragon" - Casey and Raph are just finishing their patrols when they are attacked by the Foot Cultists and barely escape with their lives. Once learning that the cultists are after something called the "Scroll of the Demodragon", they try to retrieve it, but the Foot Cultists prove too powerful and reveal that their leader is Tiger Claw, who uses the scroll to summon Kavaxas from the Netherworld. Kavaxas proves too powerful for the Turtles, April, and Casey, and they are forced to retreat and regroup, unaware of Tiger Claw's plans to use Kavaxas to resurrect the Shredder.
- "The Forgotten Swordsman" - When Karai finds herself fighting for control of her Foot Ninja against former Foot senior member Hattori Tatsu, Casey and Shinigami are badly injured in the fight for control of the mutated Kuro Kabuto, leading to where Tiger Claw regains control of it, Tatsu has his soul drained by Kavaxas, and Casey and Shini are left outside a NYC hospital to be found and taken inside by two NYPD officers for immediate medical treatment.
- "End Times" - At some point prior to the episode's events, Casey was discharged from the hospital and shown to have made a full recovery. After an attempt to prevent the revival of Shredder fails, but Donnie gathers the info on Kavaxas he needs, Casey prepares to confront Kavaxas with the Turtles and April, only for Kavaxas to begin his invasion of the living world, forcing Casey to be entrusted with Mikey's equipment to aid Raphael, Donnie, and April with confronting the various ghosts and spirits summoned from the Netherworld by Kavaxas, while Leo, Mikey, Karai, and Leatherhead go to deal with Kavaxas. During the battle, Casey helps in sending the spirit of Hattori Tatsu back to the Netherworld, while bearing witness to Master Splinter coming to aid them against Ho-Chan. After Kavaxas and Shredder are returned to the Netherworld and the invasion halted, Casey joins the others in saying their final goodbyes to Splinter before he returns to the afterlife, before turning to enjoy the beautiful sunset.
- "The Wasteland Warrior" - Though this episode takes place in an alternate timeline, Casey's skull is shown while Raphael is driving the vehicle, indicating that he died instantly after the Mutagen Bomb was set off (along with all the other humans).
- "The Curse of Savanti Romero" -
- "Monsters Among Us!" -
- "Wanted: Bebop & Rocksteady" -
Casey is pretty thin for a teenager in addition to being taller than April as well as the Turtles (though shorter than most other mutants, including Master Splinter). He has black, medium-length hair and his two front teeth of his upper jaw are missing, which he explains were accidentally knocked out by what was then his best friend. His outfit consists of a black bandanna tied around his head, a messy, maroon elbow-length shirt with a short-sleeve gray shirt and a sleeveless black hoodie over it, grayish-blue jeans, black finger gloves that stop at the forearms, and black sneakers.
- The Turtles - Before meeting the Turtles, Casey originally viewed mutants as the bad guys. However, after following Raphael into the sewers and finding out that April already knows the Turtles, he re-evaluates his opinion about mutants, gradually accepting them throughout Season 2 and especially in the following seasons. Casey seems to interact the most with Raphael and Donatello. Occasionally, he hangs out with Michelangelo and spars with Leonardo.
- Leonardo - Leonardo and Casey are close friends, though Casey seems to interact more with Raphael and Donatello. They don't really interact with each other much, but Casey respects Leo as a leader. He grows a bit closer to Leonardo during Season 3 and shows concern for the leader's well-being, especially during their stay at the farmhouse ("Eyes of the Chimera"). On the other hand, Leonardo's usually concerned about Casey's recklessness, often comparing him to Raphael and especially Michelangelo whenever he's off patrolling the city on his own, or when's he with at least one of them ("Meet Mondo Gecko").
- Raphael - Casey originally viewed Raphael as evil, but after finding they have things in common (e.g. fighting crime, having similar tempers), they eventually become best friends. Mostly, they work as partners in defeating any enemy that comes their way. However, their friendship has their ups and downs ("Newtralized!"). He also understands Raph's protectiveness over his brothers, as seen in "The Invasion, Part 1", when Casey asks Raph if April has feelings for him. Raphael refuses to answer his question, stating that Donatello also has feelings for her. During the farmhouse arc, they're often seen sparring together ("Eyes of the Chimera").
- Donatello - Though he seems closest to Raphael out of all the turtles, he's also very close to Donatello, more so during "Race with the Demon" when Casey apologizes for ditching him while doing a test run. In addition, Raph is the first turtle Casey saw ("The Good, The Bad, & Casey Jones"), Donnie's the first turtle who saw him ("Mutagen Man Unleashed"). At first, they start off as rivals for April's affection throughout Season 2. Donnie reluctantly teams up with Casey while building a racecar to defeat Speed Demon. Their rivalry awakens once again during "Riddle of The Ancient Aeons", when the Aeon gas causes them to lash out at each other (except for April and Fugitoid). Overall, their friendship improves in Seasons 4-5. During "The Power Inside Her", Casey is visibly horrified when April (Za-Naron) disintegrates Donnie with the Aeon crystal, showing that he cares about him. Afterwards, Donatello and Casey grow closer and express their concern over April's well-being ("Tokka vs. The World"), since she defeated Za-Naron single-handedly. In "Requiem", Casey injures Shredder out of grief-filled rage by crushing him under a truck, hoping to avenge Splinter's death. He's then seen silently mourning behind Donnie while the genius weeps over Splinter's body. They don't talk to each other much during the final season, though during the series finale, Donatello grows concerned about Casey's broken ribs, advising him to rest.
- Michelangelo - When they first met, Michelangelo assumed Casey was an intruder (along with the other turtles). However, after fighting the Kraang, they became allies and eventually close friends. Whenever Casey gets bored, he often asks Mikey to hang out with him ("Meet Mondo Gecko"). Both have a share for comics such as Wingnut & Screwloose, who used April's Aeon crystal to bring them to life. Whereas Mikey's brothers usually make fun of him, Casey's willing to spend time with him. However, there are times when Casey acts like Leo, Raph, & Donnie when it comes to treating Mikey, as seen in "Buried Secrets" when he doesn't believe Michelangelo's assumption about April's mom (turns out Mikey was right all along). In "Bat in the Belfry", Casey refuses to believe Mikey when he claims that Wingnut & Screwloose have escaped from his favorite comic book. Nonetheless, Casey cares about Mikey and somewhat acts like a big brother to him.
- April O'Neil - April hangs out with Casey in school. At first, April was tutoring Casey and after sometime they became good friends. Although it was revealed that Casey prefers to spend time alone with April, he's seen to hang out with her and the turtles in some episodes. Since then it has been show that Casey and April have feelings for each other. Casey shows his emotions toward April more though by crushing on her [for example in The Invasion, Part 1 when he did some graffiti on a nearby wall of him and her together]. Although in later seasons that seems to have changed. When the two of them remained alone to look after the house in Vision Quest for a week and despite Casey being flirtatious at first, when the turtles return and Casey and April are sparring, it is very clear that April doesn't see him as a love interest. And when the gang in Return to New York, taking temporary refuge in an old Pizzeria, she remarks that it is a "little cramped for her taste" before she and Casey look at each other and then look away, suggests, that the feeling is mutual, they have developed more a brother-sister kind of relationship. The Fugitoid saga episode The War for Dimension X had the two of them alone on the ship a couple of times and neither is very happy about that prospect, with Casey slamming his goalie stick into the floor and April grumbling in frustration. Overall, Casey seems to show his softer side to April more than he does with the others. In "The Good, The Bad, and Casey Jones", he admits that he cares about her while writing in his diary. After escaping New York City during "The Invasion, Part 2", April hugs him after Casey sadly admits that he couldn't find his dad and little sister. In "Buried Secrets", he expresses sympathy towards her after April considers reconnecting with her mom, even though it meant leaving the turtles behind. During "The Power Inside Her", Casey firmly believes that April is still "in there" and can defeat Za-Naron once and for all. In "Requiem", Casey is seen hugging her close to him after witnessing Splinter's death.
- Fugitoid - Casey didn't trust Fugitoid at first (along with Leo) when they met in the Season 3 finale, but he instantly changes his mind during the Season 4 premiere, when Fugitoid time-travels six months into the past, thus giving them another chance to save Earth. After temporarily defeating Lord Dregg ("Beyond The Known Universe"), he and Fugitoid become friends. They remain friends and allies until "Earth's Last Stand", when the professor reveals his secret about being the actual creator of the Black Hole Generator instead of the Kraang. Though he wasn't as furious as Leonardo was, he became disappointed and skeptical of Fugitoid's actions throughout the episode. Once the professor sacrificed himself, Casey felt internally grateful for Fugitoid bringing them back home before resuming his life on Earth.
- Splinter - Originally, Casey was afraid of Splinter due to the fact that he has a fear of rats, but has since become comfortable with being around him. Splinter has been shown to be friendly towards Casey when meeting him, as he thanked him for helping to protect his sons (the Turtles) and the lair (their home). Casey told Splinter it was no problem. Since then despite his fears, Casey has had no problem being around Splinter or being in the sewers. Though they don't interact with each other much, they were friends and Casey becomes visibly upset after witnessing Shredder murder Splinter during the Season 3 finale but was relieved it was undone. However, he become furious when his death is permanent in "Requiem", as seen when crushing Shredder with a truck out of grief-filled rage. Casey also mourned Splinter's death at his funeral.
- Dr. Cluckingsworth - At first, Casey was annoyed that there was yet another mutant in his life, sarcastically claiming that it was "just what he needed". However, he instantly changes his mind and bonds with her while saving Donnie from Speed Demon's clutches. Since then, they've become close friends. He silently bids her goodbye once they leave the farmhouse, though Donnie seems to share a closer bond with her. Casey is also impressed by her genius-level intelligence after she accidentally drinks the mutagen oil that was spilled on the road ("Race with the Demon").
- Mondo Gecko - Casey and Michelangelo befriended him at first, but then briefly hated him for taking money from the Purple Dragons and betraying their trust by working for Xever. After surviving Fishface's wrath, they got on better terms.
- Slash - Was originally wary of him due to his extremely violent nature, now they are acquaintances on better terms.
- Bigfoot - Caused her to run away into the woods when he and Leo mocked her make-over. Mikey who overheard and saw Bigfoot run off, called them out for it.
- Punk Frogs - Casey originally hated the Punk frogs because they kidnapped and locked him and April in cages, but when the fire started he saved Attila by shoving him from the base.
- Bernie - Casey was originally horrified of him due to his restless nature making him look insane, but later allied with him to save the turtles from the Dream Beavers. He then took him home after he fell asleep after the whole ordeal.
- Karai - Although they haven't had any contact or interaction, He along with April and the Turtles have attempted to help save her from the Shredder a few times. He later met her in "The Deadly Venom" when she attempted to hunt down him, the Turtles, and April by poisoning and killing them all which failed. She also kissed him as she poisoned him. In mid-season 4, they seem to be in good terms with each other.
- Bishop -
- Hun - Casey's arch-nemesis. They first met in "Casey Jones VS. The Underworld" when Hun surprised him by revealing that he was the new leader of the Purple Dragons. After easily defeating Casey during their first encounter, an angered Casey decides to follow him and incidentally discovers Shredder's (and apparently Don Vizioso's) next move.
- Mutagen Man
- Rat King
- Baxter Stockman
- Tiger Claw
- Kraang Prime
- Bebop (formerly)
- Rocksteady (formerly)
- Mom-Thing - At first, Casey assumed she had good intentions, as she was supposedly April's long-lost mother. He seemed to sympathize with April's dilemma: leave the Turtles (including himself) behind and going somewhere far away with her mom. However, he changes his mind once a terror-stricken Raphael warns them about her true identity. He then angrily demands her to leave April alone and helps both his friends defeat Mrs. O'Neil's impersonator.
- Dream Beavers
- Speed Demon
- Ho Chan
- Purple Dragons
Casey seems to be a bit arrogant, a bit flirty (at least around April), quite inattentive to his school work, and he thinks highly of himself. Even with his first encounter with April, he appears to be frequently involved with himself and the fact that he thinks little of others. But he admits that he does need a tutor, as he wishes to stay on his hockey team. And while he tended to aggravate April a bit during their tutor session, he tried in his own way to be friendly and get her to enjoy herself with something besides just books. He also shows a sense of "empathy" when she shows to be exhausted from that day, and reaches out to wipe a smudge off of her face.
During their encounter with Mutagen Man, Casey became protective over April and tried his best to watch out for her. He was also very impressed by how April fights - and he then asks if encounters like with Mutagen Man happen frequently. When she answers "too often", the idea seems to excite him. Throughout Season 2, he gets to know April better. By "The Good, The Bad, and Casey Jones", he openly admits in his journal that he cares about her, revealing that he does care about people who are considered dear to him, including his own family. Though he seems as childish as Michelangelo most of the time, after Splinter's death in "Requiem", he matures significantly. It shows that he's grown to care for Master Splinter as well.
He also shares similar personality traits with the Turtles, though he considers himself more of a solo player. Like Leonardo, he prefers to go on solo missions, putting his own life at risk. Like Raphael, he has a bad temper yet sometimes displays his soft side (especially when talking about his family and former best friend). Like Donatello, he gets frustrated easily yet also has feelings for April (until "Earth's Last Stand"). Like Michelangelo, he's extremely reckless and full of adrenaline.
In addition, Casey has a strong sense of justice, often calling out things that are unfair. He doesn't like being left behind during a fight, even though the Turtles usually consider him as a strong combatant. He also seems to have athletic intuition during combat, often using his advanced hockey skills as a reference. When he grows up, he wants to be a pro hockey player (at least during Season 2).
He is not above feeling sympathy and empathy for others. In "Newtralized!", he reassures Raphael that he won't abandon him like Slash did in "Slash and Destroy". Therefore, Casey empathizes with Raph's situation as he did lose his former best friend the year before ("Target: April O'Neil"). He is very inclusive when it comes to sparring sessions, frequently inviting Leo to join him and Raph regardless of his leg injury ("Eyes of the Chimera"). He genuinely worries whenever his loved ones are acting strange, and becomes scared whenever it spirals out of control ("The Power Inside Her"), especially when April briefly succumbs to the power of the Aeon Crystal and indirectly murders Donnie in front of him.
- Custom Painted Goalie Mask
- Skull Face Paint
- Hockey Glove
- Laird's Hockey Blocker Glove - with spikes
- Homemade Taser - a potato masher rigged with 9volt batteries on a drawer track with springs
- Padlock of Doom - a lock tied up to a handkerchief
- Bunch of Keys
- Custom Sheaths - made out of belts and duck tape
- Paint Grenades - spray cans
- Wooden Baseball Bat
- Eastman's Wooden Hockey Stick
- Wooden Goalie Stick
- Wooden Cricket Bat
- Custom Skates
- Spiky Pads
- Fire Breathing Bicycle
- Hockey Pucks
- Explosive Hockey Pucks
- Protective Cup
- "School isn't always my thing. When I graduate, I’m becoming either a pro hockey player or an international bounty hunter." - Mutagen Man Unleashed
- "Who wants a normal life anyway, right?" - Mutagen Man Unleashed
- "It happens." - Target: April O'Neil
- "My best friend since 2nd grade...never spoke to me again." - Target: April O'Neil
- "You're right. Some things are just beyond our control." - Target: April O'Neil
- "Do you know what this is? This is Casey Jones vs. Evil Robo-Ninjas! Coolest freaking thing in the universe!" - Target: April O'Neil
- "Scum-suckin' mutant freaks of the world, prepare to meet Casey Jones!" - The Good, The Bad, and Casey Jones
- "Goongala!". - (Several Episodes)
- "I'd do the same for you, Raph!...Like dozens of times!" - Newtralized!
- "No sign of 'em. They probably got Kraang-tized." - The Invasion, Part 2
- "So um...why does he sound different?" - Within the Woods
- "Sure, but when I wanted a dog, you guys were like 'no way'!" - A Foot Too Big
- "That...is great!" - A Foot Too Big
- "We didn't mean to hurt her feelings." - A Foot Too Big
- "Lookin' good, Red. Keep up all the hard work." - Buried Secrets
- "Stop it, Mikey! D'you have any idea how much this means to April? If you ruin this for her...!" - Buried Secrets
- "That's rough, Red. But I understand if you wanna go with her. She's your mom. It's just..." - Buried Secrets
- "Huh. Maybe because a giant turtle driving a hippie bus seems a little suspicious!" - Race with the Demon
- "Listen, Donnie...I'm sorry I went after Speed Demon without you...I need your sweet scientific genius, Don. Please...!" - Race with the Demon
- "I don't care about winning the race! I just want my friend back!" - Race with the Demon
- "The class is Pain 101. Your instructor is Casey Jones." - Casey Jones VS. The Underworld
- "O-Okay. Maybe I'm a little afraid of you." - Casey Jones VS. The Underworld
- "Get it together, Raph!" - The Evil of Dregg
- "That is messed up, yo!" - Earth's Last Stand
- "Leo was right! He's useless!" - Earth's Last Stand
- "So, uh, what are we going to do about this? The Earth isn't big enough for two Casey Joneses." "Hey, back off, punk!" - Earth's Last Stand
- "Yeah, sure....if you're crazy!" - Bat in the Belfry
- "Oh my gosh!" - The Power Inside Her
- "We know you're in there, Red!" - The Power Inside Her
- "Death curse? For real?" - Tale of Tiger Claw
- "Oops." - Requiem
- According to TMNT Wiki (the official Nickelodeon TMNT website), Casey was born in 1995.
- Casey's hockey stick has "Eastman" written over it as well as his arm protection has the name "Laird", the names of the Ninja Turtles creators.
- It is revealed in "Mutagen Man Unleashed" that Casey needed a math tutor in order to maintain his position on his school's hockey team, and so this ultimately led him to befriending April O'Neil.
- Casey had a best friend before meeting April and the Turtles, but they're no longer on speaking terms due to presumably similar circumstances that caused April to temporarily unfriend the Turtles ("Target: April O'Neil").
- In "The Good, The Bad and Casey Jones", it is revealed that Casey has musophobia (the fear of mice and rats). At the beginning, he was terrified of Master Splinter, as seen when he immediately fainted after their first encounter.
- When Casey was drawing himself defeating Raphael, it was in the style of the original mirage comics.
- Casey often writes in his journal about his adventures with April and the Turtles ("The Good, The Bad, and Casey Jones").
- Casey mentions his dad and little sister during "The Good, The Bad and Casey Jones", though his sister's name is still unknown.
- According to his bio on the official Nickelodeon TMNT website, Casey is left-handed. This is seen with how he holds his weapons and how he writes about the Kraang battle in "Casey Jones VS. The Underworld".
- It is revealed in "The Curse of Savanti Romero", that Casey's favorite holiday is Halloween.
- It is revealed in "Plan 10", that Casey hates Dubbed Anime.