In "Mikey Gets Shellacne," Stockman was revealed to have secured a large amount of mutagen, seeking to create an army of mutants to serve him. Unfortunately, he was sought out by Karai to be taken back into the Foot Clan when cornered by Dogpound, who he claimed he can return to his human form. As a precautionary measure, Dogpound placed a collar containing mutagen around Stockman's neck, vowing to mutate him if he double-crossed him. After Dogpound was mutated into Rahzar and the villains were defeated by the Turtles, Stockman was brought back into the Foot Clan once again, with a collar containing a set of miniature mutagen vials locked around his neck, which was meant to mutate him if he attempted another betrayal.