Hisser (voiced by Estevez Gillespie) is a snake/pillbug-like Toxic Mutant who is the 1st of his kind to battle the Mega Rangers alongside Bigs and Bluefur at the debut of the Toxic Mutants. He has the ability to burrow underground and spray toxic slime. Hisser proves to be cunning, hardy, strong and competent in battle, as he easily outmatching the Rangers until Robo Knight enters the stage, with the latter having quite some dificulty in taking him down. However, his misjudgment of the robotic warrior proves to be a fatal mistake.