Debi Derryberry character James 'Jimmy' Isaac Neutron (voice)
Megan Cavanagh character Judy Neutron (voice) / VOX (voice)
Mark DeCarlo character Hugh Neutron (voice)
Jeffrey Garcia character Sheen Estevez (voice)
Patrick Stewart character King Goobot V (voice)
Martin Short character Ooblar (voice)
Frank Welker character Goddard (voice) / Poultra (voice)
Rob Paulsen character Carl Wheezer (voice) / Mr. Wheezer (voice) / Mrs. Wheezer (voice) / Kid in Classroom (voice)
Carolyn Lawrence character Cindy Vortex (voice)
Crystal Scales character Libby Folfax (voice)
Candi Milo character Nick Dean (voice) / Britney (voice) / PJ (voice)
David L. Lander character Yokian Guard (voice) / Gus (voice)
Carlos Alazraqui character Mr. Estevez (voice)
Jim Cummings character Ultra Lord (voice) / Mission Control (voice) / General Bob (voice)
Keith Alcorn character Bobby (voice) / Kid (voice) / Control Yokian (voice)
Kimberly Brooks character Zachary (voice) / Reporter (voice) / Angie (voice) / Libby's Mom (voice)
Andrea Martin character Ms. Winfred Fowl (voice)
Billy West character Bobby's Twin Brother (voice) / Butch (voice) / Jailbreak Cop (voice) / Old Man Johnson (voice) / Robobarber (voice) / Flurp Announcer (voice) / Yokian Officer (voice) / Anchor Boy (voice) / Guard (voice)
Bob Goen character Yokian Newscaster #1
Mary Hart character Yokian Newscaster #2 (voice)
Bob Goen character Yokian Newscaster #1 (voice)
Dee Bradley Baker character Norad Officer (voice)
Greg Eagles character Libby's Dad (voice)
Jack Angel character Additional Voices (voice)
Laraine Newman character Hostess (voice)
Gregg Berger character Additional Voices (voice)
Mickie McGowan character Additional Voices (voice)
Phil Proctor character Additional Voices (voice)
