Seth Green

Milo (voice)

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

Martian Hatchling (voice)