Seth Green
Milo (performance capture)
Seth Robert Dusky
Milo (voice) (as Seth Dusky)
Joan Cusack
Mom (voice)
Dan Fogler
Gribble (voice)
Breckin Meyer
Alien (voice)
Elisabeth Harnois
Ki (voice)
Tom Everett Scott
Milo's Dad (voice)
Mindy Sterling
Supervisor (voice)
Julene Renee
Martian (voice)
Raymond Ochoa
Martian Hatchling (voice)
Robert Ochoa
Ryan Ochoa
Amber Gainey Meade
Martian
Dee Bradley Baker
Two-Cat (uncredited)
