John Cusack as Igor (voice)

Myleene Klass as Dr. Holzwurm (voice)

Robin Walsh as Dr. Holzwurm's Igor (voice)

Matt McKenna as Dr. Herzschlag (voice)

John Cleese as Dr. Glickenstein (voice)

Steve Buscemi as Scamper (voice)

Sean Hayes as Brain (voice)

Eddie Izzard as Dr. Schadenfreude (voice)

Jay Leno as King Malbert (voice)

Jennifer Coolidge as Jaclyn / Heidi (voice)

Molly Shannon as Eva (voice)

James Lipton as Himself

Christian Slater as Dr. Schadenfreude's Igor (voice)

Arsenio Hall as Carl Cristall (voice)

Jess Harnell as Announcer / Royal Guard #2 (voice)

Zoë Bright as Blind Woman / Killiseum Fan #1 (voice)

Sophia Eraklis as Blind Orphan #1 (voice)

A. Cheron Hall as Blind Orphan #2 / Blind Orphan #4 (voice)

Alexander Leondis as Blind Orphan #3 (voice)

Michael Leondis as Blind Orphan #6 (voice)

Nicole Leondis as Blind Orphan #7 (voice)

Juliana Leondis as Blind Orphan #5 (voice)

Robin Tisserand as Blind Orphan #8 (voice)

Paul Vogt as Buzz Offmann (voice)

Frank Welker as Animals' vocal effects (voice) (uncredited)