The Turtles subsequently spent the first half of the fourth season working to undo this turn of events. While they are unable to save the original versions of the Mutanimals and the others, they are able to save a second version of them in "Earth's Last Stand" where thanks to Splinter getting the heads up and intercepting Shredder's attack, the Turtles destroyed the timer to the Heart of Darkness, causing Earth's secondary annihilation to never occur. In "Mutant Gangland," the Mutanimals with Mondo Gecko as their newest member stop the Fulci twins from obtaining new-and-improved weaponry. Rockwell telepathically sees into one of their minds and is shocked to learn that they are engineering these weapons to hunt down and destroy all mutants. The quarter head to warn the Turtles about this dangerous threat against all mutant-kind. Noticing that Pigeon Pete is missing, Donatello asks the Mutanimals where he is to which Slash replies "We don't talk about Pigeon Pete", indicating that soon after their victory of defeating the Triceratons, Pigeon Pete left the team for unknown reasons. In "Requiem," the Mutanimals are in their hideout working how to plan their next attack on Super Shredder with the aid of Karai and Shinigami. They are interrupted by the arrival of Super Shredder who burns their hideout and defeats them with ease. They are rescued by April and Casey while Splinter and Leonardo save a seriously hurt Karai via CPR. Slash goes with Raphael, Splinter, April and Casey to track down Super Shredder while Leatherhead, Mikey, Leo, and Donnie go fight Fishface, Rahzar, Bebop, and Rocksteady at the amusement park. However, Slash is no match for Super Shredder's might and is knocked out. Leatherhead manages to beat Rahzar by dragging him underwater. In the fourth season's finale titled "Owari," Rockwell, Leatherhead, Slash, and Pigeon Pete all appear at Splinter's funeral. In "The Big Blowout," the Mutanimals (with Mona Lisa as their newest member) fights alongside the turtles, their 1980s counterparts, April, Casey, Karai, and Shinigami in a battle against the 1980s counterparts of the Shredder, Krang, and the present Bebop and Rocksteady. They soon face the return of Traag and Granitor until Bebop and Rocksteady came to save everyone.