The Mighty Mutanimals are a group of heroic Mutants formed by Jack Kurtzman and lead by Slash, who protect the city from crime, evil mutants, and alien threats. They are also allied with the Ninja Turtles. They debuted in Battle for New York. They have six members, Slash (the leader) Leatherhead (second in comand) Dr. Rockwell (the brains) Pigeon Pete (the spy) Mondo Gecko and Muckman.
Jack Kurtzman encountered Slash while hiding from the Kraang and became his benefactor to find other mutants like him in order to help fight the Kraang. Slash was able to enlist Dr. Tyler Rockwell, Leatherhead, and Pigeon Pete to form the Mighty Mutanimals.
After saving a couple of humans from being mutated, the turtles did battle with a squad of Kraang Droids, but they were eventually cornered. As the Turtles were about to get blasted, the Mutanimals rushed in to save them, crushing the squad of droids. Afterwards, Slash greeted the turtles and introduced his new team. As the other turtles humbly greet their friends, Leo's feelings are overshadowed by bitterness towards Slash regarding their first encounter. Slash insists that the mutagen clouded his mind at that time, though Leo is not satisfied. The turtles go with them to meet their benefactor at Leatherhead's suggestion, but unbeknownst to all on them, the Kraang were following them. When the turtles and Mutanimals make it to the hideout, they discovered that the benefactor in none other than Jack Kurtzman, who says that when the turtles were absent he tracked down the noble mutants who are now the Mighty Mutanimals. Kurtzman suggested that now that the turtles are back, they all can stop the Kraang invasion together, to which Leo and Slash protest. Kurtzman informs the mutants that the Kraang are planning to fire a gigantic mutagen missile at the earth, mutating it into another Dimension X. Shortly, a huge argument between the turtles and Mutanimals begins as the Kraang finally find them and invade the Mutanimals' lair. Both teams try to fend off the aliens as Kurtzman tries to salvage his Kraang intel. Just as Kurtzman grabs the drive, he is shot and gravely wounded. Leo and Slash order their teams to retreat to get Kurtzman some medical help. They take him back to the turtles' temporary "lair" at the abandoned pizzeria. There, a weak Kurtzman gave them the drive with all of his Kraang intel and told both teams that they must work together to stop the Kraang, and then faints. This leaves Leo wondering if he died, but Splinter checked his pulse and said he was fine. The teams initially try to team up as Kurtzman wanted, but Leo and Slash couldn't agree on whether they should use ninja stealth to disarm the missile or do a ground attack. Raphael suggests that the only way it will work is if they do both, to which neither leader agrees. The Mutanimals proceed to their ground attack as Kraang Subprime arrives, which apparently serves as a distraction as the turtles were doing their stealth mission to disarm the missile (coincidentally the plan Raphael suggested). The Mutanimals attempt to hold Kraang Subprime back to prevent him from launching the missile, but they are unsuccessful and the missile is launched with the turtles still on it. However, Donatello quickly reroutes the missile to the heart of the sun and he and his brothers jump off and glide back down to earth's surface using their turtle flyers. The turtles use their garbage cannons to help out the Mutanimals, forcing Kraang Subprime and his troopers to retreat. Afterwards, the turtles and Mutanimals reconcile and this time congratulate each other on stopping the missile together. Even Leo told Slash that he was impressed by him, to which Slash asserts that he's a different turtle than he once was. The two leaders shake hands and decide to proceed to the next part their mission to stop the Kraang invasion: storming TCRI and entering Dimension X to save the captive mutated citizens on New York. Like so, the Mutanimals force their way into TCRI, crushing everything that gets in their way. Slash covered Rockwell so he can open the portal to Dimension X and allow the turtles to enter. He succeeds and the turtles enter Dimension X, but are followed by Kraang Subprime. Meanwhile, Slash, Leatherhead, and Pigeon Pete and fending off more and more Kraang forces while Rockwell guards the portal in an effort to prevent them from closing it. Unfortunately, they get to Rockwell and knock off his psychic helmet. Slowly, the Mutanimals were starting to lose the fight and when Rockwell's life was threatened, Slash was forced to give up and allow the Kraang to close the portal, trapping the turtles in Dimension X. The Mutanimals are then imprisoned by the Kraang, causing Slash to question his value as a leader. Leatherhead encourages Slash, telling him that he saw him save humans as well as his fellow mutants and that he is a good soul. Soon after, Rockwell managed to focus his diminished psychic to set them free. The Mutanimals once again attacked and Rockwell reopened the portal, allowing the turtles to teleport out of Dimension X after saving the citizens of New York and an unexpected fight with Kraang Subprime. With the Kraang invasion put to a stop, the turtles and Mutanimals meet once more on a rooftop. They congratulated each other on their successful mission. Raph nudges Leo into admitting that Slash did good and that everyone deserves a second chance. Slash tells him that he just tried to model himself after Leo: the greatest leader he ever knew. The two then “bro shake” and Leo declares that it is time to celebrate, prompting everyone to shout a hearty BOOYAKASHA!!!
The Mutanimals arrive at the docks to intercept a deal between Tiger Claw and the Fulci Twins and apprehend the criminals. Unfortunately, the Fulci Twins get away and Tiger Claw abducts Slash and Rockwell as they may have some value to the Shredder. The clan leaves the scene after ramming Pete and Leatherhead into the nearby lake with a van. Leatherhead and Pete show up at the turtles’ lair, informing them of the situation and asking them to help rescue Slash and Rockwell, which the turtles agree to. In Shredder’s lair, he decides to have Baxter Stockman test the mind control serum (complete with the chemicals Tiger Claw received from the Fulci Twins) on the newly abducted Slash and Rockwell. Stockman then created mind controlling worms by using the serum on normal earthworms and then put one each inside of both of the mutants’ bodies. Shortly afterwards, they escaped Shredder’s and were being chased down by Foot Bots. The turtles, Leatherhead, and Pigeon Pete come to their aid, destroying the androids and taking the abductees back to their lair. In the lair, Slash and Rockwell are trying to explain what Shredder did to them, but can’t quite remember the details. Suddenly, when Slash hears Splinter say the word “water” he snaps and strikes Splinter as a result of the worm’s brain programming. Rockwell reiterates with the same reaction shortly after, and they both proceed to attack the turtles, Leatherhead, and Pigeon Pete. A brainwashed Slash remembers Shredder’s orders to bring him one of the turtles and ends up throwing a knock out gas bomb at Raphael. He and Rockwell then steal the Party Wagon with Raph in tow, prompting the other turtles, Pete, and Leatherhead to follow them in the newly repaired Shellraiser.They end up losing the duo but know they are headed for Shredder’s lair. The group successfully breaks into the lair, but are encountered by Shredder, Stockman and the brainwashed Slash, Rockwell and now Raphael. At Shredder’s command they all attacked the heroes as they were trying to get through to them. After Leo demonstrated that they needed to regurgitate the worms to break the mind control, the others followed his example and each of they were freed. All of the turtles and Mutanimals then used the opportunity to gang up on the Shredder in an attempt to bring him down. Shredder held his own for a great deal of the fight, but was seemingly crushed by a giant statue Slash and Leatherhead purposely tipped over. When Tiger Claw and a squad of Foot Bots enter the room, the turtles use their ninja smoke bombs to help everyone escape. Back at the Turtles’ lair, Slash gives a sincere heartfelt apology to Splinter for his actions toward him while under mind control and asked for his forgiveness, but Splinter told him that there is nothing to forgive as his mind was not his own at the time.
Slash and Rockwell were investigating the north side of the sewers for a mysterious “Dino Man” making headlines while Leatherhead and Pigeon Pete searched the south side. Rockwell soon began to sense a foreign, alien presence lurking among them. That presence crashed in from above them who turned out to be the Triceraton Sergeant Zog, who was not thinking clearly due to his constant breathing of earth’s oxygen. He attacks Rockwell, prompting him and Slash to attack him. Incredibly, none of their attacks did nothing to Zog as he ravages them and leaves the area, leaving Slash badly injured. Rockwell later telepathically contacts Raphael (who was on Shredder patrol at the time), asking for help. Raphael meets him and Slash in the sewers, who inform him of the creature that attacked them and explain that he is an alien. Raphael takes it upon himself to find this “Dino Alien” and take him down, but Rockwell warns him that the Dino Man is possibly the most powerful creature they have ever encountered. Raphael then tells them both to go back to lair so Splinter can help them recover. When the turtles don’t hear from Raph after so long, Rockwell telepathically informs them that he is going after the Dino Man. Once they arrive at the lair, Rockwell and Slash tell Leo, Donnie, and Mikey that Raph’s choice of going after him alone was not wise.
Leatherhead visits Slash and Rockwell, who are still recovering from their encounter with Zog in the turtles’ lair. He thanks Splinter for caring for his friends. When the turtles bring Bishop to the lair, Leatherhead goes berserk at the sight of seeing another “Kraang”, but the turtles hold him back and assure him that Bishop is on their side. Leatherhead did not trust him, but Mikey convinced him that he has to trust him for now, so Leatherhead cooperated. He was informed by the Leonardo of the Kraang’s plans once again rise the newly repaired Technodrome to invade again, and participated in Leo’s plan to stop them. Raph, Mikey, Donnie, and Leatherhead took the turtle sub to prevent the dome from rising, while Leo, April, Casey, and Bishop prepare to take it down using the Turtle Blimp if they are unsuccessful in stopping the Technodrome from rising. The drome ends up rising shortly after the sub-team infiltrates it and Leo gives them 2 minutes to blow it up before the blimp team does. Unfortunately, the sub team are detected and detained by the Kraang. From the outside, the blimp team crashes the blimp (which is filled with explosives) into the Technodrome, to allow an opening for them enter using their Turtle Flyers and to help rescue their friends. They save the sub team shortly after Captain Mozar broadcasts a message to the people of earth. Leatherhead and Bishop stay behind to buy the rest of the team some time reach the hanger and steal a stealth ship to get off the Technodrome. After they have successfully left the dome, Bishop and Leatherhead escape as well, minutes before the Triceratons destroyed it with Kraangs Prime and Subprime still inside. Afterwards, Leo called April, saying that he wanted her and Leatherhead to get Splinter and the rest of the rest of the Mutanimals, as they would need all the help they can get in stopping the Triceratons.Later that night, all of the Mighty Mutanimals, complete with the fully recovered Slash and Dr. Rockwell, and their new members Muckman and Mondo Gecko, come with April and Splinter to aid the turtles, Casey, and Bishop in stopping the aliens from activating the black hole weapon. All of the heroes fight a squad of Triceraton troopers who are guarding the scientists who are preparing the black hole weapon for activation. They were holding their own for the most part (except for Muckman and Mondo Gecko), but Splinter realized that they were losing valuable time to stop the black hole weapon, so Leo ordered Slash and Leatherhead to take it down. However, Leatherhead was preoccupied with a Triceraton. So Slash attacked the weapon’s main control panel, managing to do significant damage to it before Mozar came and trapped him, Rockwell, Leatherhead and Casey in containment bubbles and abducts Mikey. Mozar teleported away while dozens of more Triceraton soldiers teleported to location, forcing the remaining heroes to retreat and find a way to save them and the earth. The captive Mutanimals remained their up until they met their doom along with the rest of the earth by getting sucked away into the oblivion of the black hole.
Professor Zayton Honeycutt used his space ship, the Ulixes, as a time machine to travel six months into the past, long before the recent tragedy occurred.
Repeating the events of the Season 3 finale, the Mutanimals fought alongside the Turtles, Splinter, April, Casey and the Foot Clan in defeating the Triceratons, only for this time, their efforts were successful. As they witness the past Fugitoid take off with the past Turtles, Casey and April, Slash points out that it was one of the weirdest days he's seen. The Mutanimals were seen heading back home as the Turtles, April and Casey offer to fill in Splinter on their space adventure.
The Mutanimals, minus Muckman and Pigeon Pete, chases after the Fulci Twins, who were delivering the Anti-Mutant Weapons to Don Vizioso. When Donnie and Mondo Gecko was held captive by Don Vizioso and the Fulci Twins, Slash, Leatherhead, Rockwell and Raph fought the Hammer while Leo and Mikey freed Donnie and Mondo Gecko and takes on Don Vizioso and his men.
The Mutanimals teamed up with Karai and Shinigami to take down the Foot Clan but their lair was destroyed when they tried to stop Super Shredder. After Shinigami stays with Karai, who was injured during her battle against Super Shredder, Slash goes with Splinter, April, Casey and Raph to take on the Super Shredder himself while Leatherhead goes with Leo, Donnie and Mikey to take on Rocksteady, Rahzar, Fishface and Bebop on Coney Island. As Slash tries to fight the Super Shredder, he was beaten brutally and buried under a huge rubble but survived the fight while Leatherhead managed to defeat Rahzar on Coney Island. It is unknown what happened to Slash and Leatherhead after Shredder killed Splinter.
The Mutanimals attends Splinter's funeral, bidding farewell to their wise ally, Master Splinter.
Slash, Leatherhead and Mondo Gecko caught Bebop and Rocksteady, who were sent by the 80's counterparts of the Shredder and Krang to steal Kraang crystals at TCRI. Unfortunately, the Foot Soldiers from the 80's dimension attacked Slash and Leatherhead and Bebop and Rocksteady got away with Shredder. Later, the Mutanimals joined the turtles, April, Casey, Karai, Shinigami and the '80s Turtles in taking down the '80s Shredder and Krang but they must deal with Traag, Granitor and a horde of rock soldiers until Bebop and Rocksteady (who discovered '80s Shredder and Krang's true plan to destroy the Earth) came to the rescue, saving the entire city.
Founding members (Battle for New York):
- Slash - The team leader.
- Leatherhead - The second-in-command.
- Dr. Tyler Rockwell - The Brains.
- Pigeon Pete - The Spy.
- Ninja Turtles
- Hamato Yoshi / Splinter
- April O'Neil
- Casey Jones
- Foot Clan (Karai’s faction)
- Zayton Honeycutt / Fugitoid
- Earth Protection Force
- 1987 Ninja Turtles
- The Kraang
- Foot Clan (Shredder’s faction)
- Oroku Saki / Shredder / Super Shredder / Undead Shredder (deceased)
- Chris Bradford / Dogpound / Rahzar (deceased)
- Xever Montes / Fishface
- Takeshi / Tiger Claw (formerly)
- Baxter Stockman / Stockman-Fly
- Ivan Steranko / Rocksteady (formerly)
- Anton Zeck / Bebop (formerly)
- Elite Footbots
- Foot Cultists (formerly)
- Triceraton Empire
- Purple Dragons
- The Italian Mafia
- 1987 Foot Clan
- Both Mutanimals and Turtles' "brains of the group" wear purple as a signature color.
- Half of the Mutanimals started out as animals that were mutated into greater forms (Slash, Leatherhead, and Pigeon Pete), while the other half were once humans that became mutants (Dr. Rockwell, Jason, and Garson Grunge).
- Four of the Mutanimals members were used in other incarnations of the team, Leatherhead in the Archie comics, Pigeon Pete in the IDW comics and both Slash and Mondo Gecko in both the Archie and IDW comics.
- Dr. Rockwell and Pigeon Pete remain the only mutants in the 2012 series who's original forms were never seen.
- Muckman, as mutant garbage, is the only Mutanimal whose mutant form is not animal-based.
- The Mutanimals were given more background development in The Meeting of the Mutanimals, a story arc that appeared in Teenage Mutant Ninja Turtles: Amazing Adventures. In this arc, Slash and Pete were the two founding members, and they later rescued and recruited Leatherhead and Rockwell. The story also expanded on Slash's reverence for Splinter's teachings and how they influenced his leadership and organization. However, like the rest of Amazing Adventures, this arc does not share canon with the TV series, and its details remain apocryphal to the TV series.