Casey is an adult, well-built man with long black hair. He is usually dressed in a deep red T-shirt and long dark blue sweatpants with white trim. Often, brown gloves are worn on his hands.
In Back to the Sewer, his usual clothing is a red t-shirt that has light beige sleeves, black jeans tied with a brown belt and brown shoes. His hair is darker as well.
Contrary to the 1987 series, Casey Jones becomes a regularly recurring character in the 2003 TV series. In this series, Casey has his longest-lasting appearance in TMNT pop culture. He talks in a Brooklyn accent. This incarnation's personality is on par with Raphael's, as he is frequently shown fighting and is impulsive. As in the Mirage comics, his his first encounter with the Turtles involves Raphael.
In Meet Casey Jones, Raphael first encounters Casey while the vigilante tries to stop a mugging. Raphael stopped him from seriously injuring a gang of Purple Dragons, and while doing so sees a lot of himself in Casey. Raphael tries to reason with Casey to prevent him from letting his anger get the best of him. The two fought with each other, but were brought back to their senses by their common enemy. Though initially uninterested in what he had to say, Casey eventually bonds with Raphael and they soon become best friends by their very similar way of seeing the world. Casey was at that occasion formally (re-)introduced to the Ninja Turtles; after that, they became close friends and allies.
Casey's backstory is fleshed out over the course of the series. Casey's hatred of the Purple Dragons is rooted in an incarnation in his childhood. While Casey was still a kid, his father Arnold Jones, Sr. refused to pay protection money to the Purple Dragons and their leader Hun. His father's shop was burned down as a result, and a teenage Hun threatened Casey to tell his father to pay up next time. ("Fallen Angel") Despite being threatened not to, Jones, Sr. subsequently went to the police, but with no success; it is implied that Hun later killed him for trying to turn them in. For this reason, Casey has a very particular dislike for Hun. Dragons Rising features a flashback of Casey's father telling him the importance of doing "the right thing." In the present, Casey relates this to Hun, who replies that he "was dead wrong!" As a result, Casey developed a deep hatred for crime, the Purple Dragons in particular, and vowed to get revenge.
Arnold Casey Jones, Jr. — first name rarely spoken (except by his mother) — it is revealed in "The Lesson" that he first met the Turtles as a kid, although neither the Turtles nor Casey himself are aware of this fact. During a trip to the surface, the young Turtles witness bullies picking on young "Arnie." Disguising themselves as human children they tried to teach him ninjutsu, however, their unique perspectives and attitudes lead to more trouble than help, so they do not succeed. However, in the end their lessons inspired him to stand up to the bullies in order to save a friend, and (in a bit of foreshadowing) using one of their own hockey sticks to defeat them proclaiming they were no match for "Arnold Casey Jones!".
As he grew older, Casey became a vigilante and started hunting down crooks and thugs — particularly Purple Dragons — in the streets. Incidentally, fate brought him across the path of the turtles (specifically, to Raphael) once again. Casey Jones would help the Turtles out with various operations and the Turtles would return the favor.
Despite his lack of intelligence and apparent incompetence, he was early on in the series referred to by Hun as "Our (the Purple Dragon's) greatest enemy," and a fighting tournament was held to see which Dragon would have the honor of killing him, indicating how serious a threat the criminal underworld views him as.
In the series, in contrast to earlier representations, Casey has a good heart and is a loyal friend, but is easily enraged and occasionally bumbling. He loves motorcycles. In a symbolic way, he sees the Turtles as the little brothers he never had. As such, he often comes to their aid against The Utrom Shredder, the Foot Clan or other enemies. His main catchphrase as in the Mirage comics is the battle cry "Goongala!". "The Lesson" reveals Casey's modern-day battle cry originated from his childhood where he had an encounter with the Turtles. A young Michelangelo, taught him to shout "Goro Goro Sama!" (literally, "Mr. Thunder"), which by means of misunderstanding and incorrect pronunciation Casey ultimately garbled into "Goongala!".
Through the Turtles, early on he met April O'Neil, for whom he quickly developed a romantic attraction. However, their conflicting personalities lead to frequent arguments at first. Over time, a serious relationship develops. Casey is initially "only" a street fighter and not a true martial artist, but he is a strong and capable friend of the Turtles, who knows how to defend himself well. Also in some episodes Casey's family from the Mirage comics is presented in more detail, especially his mother and his cousin Sid.
In Fast Forward, the Turtles and Splinter are transported to 2105, and it is revealed that Casey and April got married. Their line of descendants leads up to their great grandson Cody Jones in the year 2105 the heir to O'Neil Tech, a company created by April, Casey and Donatello after the turtles return to their own time, who has become one of the Turtles' greatest fans. One of Cody's inventions, the Turtle X armor, resembles Casey's hockey mask.
Casey, now 28, appears in Back to the Sewer. He and April have been taking care of the Turtles' lair during their year-long absence, and during this time Casey was brain-washed by Khan, a member of the Foot Clan. In the end, things get back to normal, and Casey proposes to April. In the finale "Wedding Bells and Bytes", he ends up marrying April, with serving Raphael as his best man and Michelangelo as the maid of honor, many recurring characters being in attendance and the ceremony performed by the Fugitoid.
Due to the change in art, Casey resembles the version of himself from the TMNT movie, complete with the black hockey outfit he wears when out fighting crime with the Turtles.
4kids TMNT Blog post with concept art of Casey's various outfits can be viewed here.
Despite being somewhat unintelligent and seemingly incompetent in some things, Casey has shown himself to be a very thoughtful and kindhearted man who would do anything for those he cared about. However his lack of wits is not his only fault, he is also incredibly aggressive, reckless and impulsive. His aggression is noted by Raphael who said that Casey was as angry as he was.
- He has a farm in the countryside left to him by his grandmother.
- In the 13th episode of season 3, "The Lesson", Casey's modern-day battle cry originated from Mikey, who taught him to shout "Goro Goro Sama!" (literally, "Mr. Thunder"), which Casey ultimately garbled into "Goongala!"
- Casey's favorite food has been stated to be Italian, Mexican, pretzels and beverages.
- Casey's favorite color is green.
- Casey acquired some basic martial arts skills as an unwitting stooge of Master Khan during the year the Turtles spent in the future. However, he still prefers to go into combat with his battering equipment.
- Favorite music is Rock 'n' Roll.