Debi Derryberry

Character: James 'Jimmy' Isaac Neutron (voice)

Megan Cavanagh

Character: Judy Neutron / VOX (voice)

Mark DeCarlo

Character: Hugh Neutron / Pilot / Arena Guard (voice)

Jeffrey Garcia

Character: Sheen Estevez (voice)

Patrick Stewart

Character: King Goobot V (voice)

Martin Short

Character: Ooblar (voice)

Frank Welker

Character: Goddard / Poultra (voice)

Rob Paulsen

Character: Carl Wheezer / Mr. and Mrs. Wheezer / Kid in Classroom (voice)

Carolyn Lawrence

Character: Cindy Vortex (voice)

Crystal Scales

Character: Libby Folfax (voice)

Candi Milo

Character: Nick Dean / Britney / PJ (voice)

David L. Lander

Character: Yokian Guard / Gus (voice)

Carlos Alazraqui

Character: Mr. Estevez (voice)

Jim Cummings

Character: Ultra Lord / Mission Control / General Bob (voice)

Keith Alcorn

Character: Bobby / Kid / Control Yokian (voice)

Kimberly Brooks

Character: Zachary / Reporter / Angie / 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)

Mary Hart

Character: Yokian Newscaster #2 (voice)

Bob Goen

Character: Yokian Newscaster #1 (voice)

Dee Bradley Baker

Character: Norad Officer (voice)

Laraine Newman

Character: Hostess (voice)

John A. Davis

Character: Octapuke Kid / Guard / Bennie (voice)

Paul Greenberg

Character: Guard (voice)

Mark Menza

Character: Yokian Incubator Operator (voice)

Jeannie Elias

Character: Little Girl / Camera Person (voice)

Michael Hagiwara

Character: Chris (voice)

Richard Allen

Character: Digital Voice (voice)

Brian Capshaw

Character: Screamer (voice)

Cheryl Ray

Character: Screamer (voice)

Matthew Russell

Character: Hyperactive Kid / Arena Yokian (voice)