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)

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)

Jeannie Elias

Little Girl / Camera Person (voice)

Michael Hagiwara

Chris (voice)