Major Story Arc
When Maligna set her sights on invading and strip mining Earth she sent her henchmen Scul and Bean and a small army of Malignoids to Earth, where Null, the man who betrayed the human race made arrangements to stop Earth's best defense the Teenage Mutant Ninja Turtles. In South America, Maligna's first attack takes place when an asteroid full of malignoid larvae crash on a beach, the malignoids proceed to devour everything in their path, but the insectoid larvae are dispatched by Jagwar, Dreadmon, and Ray Fillet, but with the turtles captured it was obvious that this was merely an inconveniance for Maligna. Word of the invasion reached Dimension X, where Leatherhead who had joined the Intergalactic Wrestling Federation had heard of his homeworlds plight and quit the IWF so he could fight for Earth, he was joined by fellow IWF wrestlers Wingnut and Screwloose, and with the help of Cuddley the Cowlick made their way to Earth. Together with the Teenage Mutant Ninja Turtle Raphael, the Mighty Mutanimals fended off Maligna's invasion, and rescued the Ninja Turtles, a new Mutant team of animals was born, one that seemed as tough as their friends the TMNT. Fighting against Null's forces the Mutanimals soon found themselves pitted against Null's Four Horsemen, Death, Famine, War, and Pestilence, the Horsemen of Null proved too much for the Mutanimals to face alone, and the team once again joined with the Teenage Mutant Ninja Turtles.
Old Hob's Army
After recovering from a bullet to the chest by Baxter Stockman. Old Hob finds Slash washed up on shore after his defeat to the Turtles. Hob decides it's time for the mutants to fight back and defend themselves from the humans seeking to use them as slaves. His first order of business is to reconcile with Splinter and the Turtles. He does this by offering his help to Splinter to rescue Leonardo whom has been captured by the Foot Clan, in return that Splinter and the Turtles join him side by side in the formation of his mutant army. Their first attack against the Foot ends in failure, as they learn that Leonardo has been turned.
Hob and Splinter begin to work with each other as Splinter breaks into Stockgen to steal Mutagen for him as part of their deal; Hob then blows up the building. They stage another attack against the Foot to win back Leonardo. Hob attacks with a blaze of fire power assisted by Slash whom manages to defeat Hun, while the Turtles battle for their brother against Shredder and the Foot. Karai appears with two mutants of her own being Rocksteady and Bebop. The two groups manage to rescue Leonardo and fight their way out of the strong hold with some additional help, but Splinter is injured by Shredder. Old Hob secures their escape by lobbing a grenade towards Rocksteady and Bebop whom are in hot pursuit. The Turtles then leave to Northampton, while Hob remains in the city continuing his quest to build a mutant army.
Hob and Slash manage to kidnap and gag a former employee of Stockgen named Lindsey Baker. Hob needs her due to his first creation, the imbecilic Pigeon Pete, being a failed experiment. He reveals that a sample of Splinter's mutated blood is in his possession. Slash uses it and becomes more intelligent being able to form coherent sentences and now can also understand Baker's scientific explanations.
The Mutanimals Are Formed
Prior to their battle against the Foot Clan. Hob stages a meeting with Splinter and the Turtles. He reveals that he has mastered creating mutants with two new creations being Herman the Hermit Crab and Mondo Gecko. Some time earlier, Hob sends Pete to get more animals to bolster his ranks. Instead, Pete runs into Rocksteady and Bebop not realizing they're enemies.
Rocksteady and Bebop follow Pete and they find the Turtles and Hob. Before a fight can begin, Hob tries to convince them to join his army pointing out that Shredder only looks at them as slaves, and together they can look after themselves forgetting the humans. Rocksteady reveals that they are half-human. Hob then responds by shooting Rocksteady in the face, and next shooting Bebop in the stomach which begins an all out battle with both sets against the two powerful half-mutants.
During the fight Mondo is swatted around by Rocksteady, Slash battles him next but is later injured by a hurling car. Alopex and Nobody join the fray to help the Mutanimals but are easily dispatched as well. Hob directs the battle as best he can until he's about to be killed by Rocksteady. Splinter rescues him and from there a plan is put together that results in Mondo Gecko electrocuting the two brutes. Even after this, Rocksteady and Bebop are not defeated, then Hob orders Herman to fire all his weapons which results in dropping a building on the two powerful monsters. Hob forgives Pete for the mistake and they all leave.
Attack on Technodrome
Old Hob prepares to lead the Mutanimals against the Foot Clan with the Turtles led by Splinter assisting him. The remaining Turtles decide it's best to join Donatello as he plans to face Krang and stop him from terraforming the planet. Old Hob is displeased over this but goes on to battle the Foot with only Splinter representing the Turtles.
The Mutanimals blast their way into the Foot Clan's stronghold which is being guarded by Karai, Hun, and a few ninjas. Hun recognizes Slash and engages him for being "suckered punch" in their last encounter only to be bested by Slash again. Mondo Gecko faces off against Karai but is set up to be killed until Splinter saves his life. Splinter then engages Karai in one on one battle; Hob takes this moment to gun down a couple of ninjas and then manages to steal Shredder's supply of mutagen. Without warning Splinter, he orders the Mutanimals to follow him leaving Splinter to face the Foot Clan alone, due to the Turtles not honoring their part of the alliance while he lived up to his end of the bargain the entire time. Slash feels this isn't right, but leaves with Hob anyway looking back on Splinter continuing his fight with Karai.
- Raphael: Raph was actually one of the teams original members, but he left to rejoin his brothers immediately after the Mutanimals first mission.
- Juntarra: Jagwar's mother, she was held captive by Null and the Four Horsemen for a time, she was crucial in the TMNT and Mutanimals victory over Null and the Horsemen. She remained with the team for a short while.
- Kid Terra: A former enemy of the TMNT and many of the Mutanimals members, Kid Terra reformed and became a close ally to the Mutanimals.
- Slash: He is the teams true 8th member, though his stay with the group was short lived due to every other member of the team being murdered while he was away.
- Candy Fine: Hangs out with the Mutanimals after she and Mondo Gecko reconciled.