Grey DeLisle

as Mandy / Castigator (voice)

Greg Eagles

as Grim / Sperg (voice)

Richard Steven Horvitz

as Billy / Billy's Dad (voice)

Vanessa Marshall

as Irwin / Mouse (voice)

Dee Bradley Baker

as Alien Moonbeast / Alien Werewolf / Moonthing (voice)

Jeff Bennett

as Alien #1 / Rat (voice)

Chris Cox

as Meadowberry / Corporal / Postal Slob (voice)

Jennifer Hale

as Billy's Mom / Stinky (voice)

Tom Kenny

as Dr. Brainiac / Alien Pilot / Wiggly / Waiter (voice)

Mr. Lawrence

as Alien #2 (voice)

Julian Stone

as Sir Raven (voice)