Debi Derryberry
James 'Jimmy' Isaac Neutron (voice)
Megan Cavanagh
Judy Neutron / VOX (voice)
Mark DeCarlo
Hugh Neutron / Pilot / Arena Guard (voice)
Jeffrey Garcia
Sheen Estevez (voice)
Patrick Stewart
King Goobot V (voice)
Martin Short
Ooblar (voice)
Frank Welker
Goddard / Poultra (voice)
Rob Paulsen
Carl Wheezer / Mr. and Mrs. Wheezer / Kid in Classroom (voice)
Carolyn Lawrence
Cindy Vortex (voice)
Crystal Scales
Libby Folfax (voice)
Candi Milo
Nick Dean / Britney / PJ (voice)
David L. Lander
Yokian Guard / Gus (voice)
Carlos Alazraqui
Mr. Estevez (voice)
Jim Cummings
Ultra Lord / Mission Control / General Bob (voice)
Keith Alcorn
Bobby / Kid / Control Yokian (voice)
Kimberly Brooks
Zachary / Reporter / Angie / Libby's Mom (voice)
Andrea Martin
Ms. Winfred Fowl (voice)
Billy West
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)
Mary Hart
Yokian Newscaster #2 (voice)
Bob Goen
Yokian Newscaster #1 (voice)
Dee Bradley Baker
Norad Officer (voice)
Laraine Newman
Hostess (voice)
John A. Davis
Octapuke Kid / Guard / Bennie (voice)
Paul Greenberg
Guard (voice)
Mark Menza
Yokian Incubator Operator (voice)
Jeannie Elias
Little Girl / Camera Person (voice)
Michael Hagiwara
Chris (voice)
Richard Allen
Digital Voice (voice)
Brian Capshaw
Screamer (voice)
Cheryl Ray
Screamer (voice)
Matthew Russell
Hyperactive Kid / Arena Yokian (voice)