Johnny Depp as Skullhead, able to peel his own skin for disguise purposes.
Zachary Gordon as Sreedo, the youngest of the Mutant Men who uses pyro-telekinesis.
Wally Wingert as Patchwork, the series' comic relief who can take himself apart.
Pete Browngardt as Medic, has healing powers and occasionally shot in the arm.
Jeffory Tambor as Shaggy Longlocks, able to extend hair at 10,000 feet.
Kevin Conroy as Green Bean, who can turn himself into vegetation.
Harrison Ford as Toolbelt, able to morph into various tools.
Fred Tastasciore as Horseman, who can remove his head.
Frank Welker as No-Mouth Nick, who literally has no mouth but Skullhead can translate his mumblings.
Sean Connery as Black Iron, leader of the Global Mutant Resistance.
Tim Curry as Beige Shadow, tyrannical ruler of the world and anti-mutant activist, who always tries to send the Mutant Men to his Moon Prison and exterminate all mutants.
Charlie Adler as Inkling, Beige Shadow's cousin and henchman.