After promising and failing Shredder time and again to deliver a mutant army to take down the Turtles, Shredder decides he's had enough and mutates Stockman into a pest, Stockman-Fly. Realizing the Turtles have developed retro-mutagen that can mutate him back into a human, he hunts them down. The Turtles better have more than a fly-swatter to take down this mutant pest. Not only does Stockman-Fly possess super mutant strength and the ability to fly, he can also fire highly toxic acid vomit that will make the Turtles want to hibernate back into their shells.