 John CusackIgor (voice) | Igor (voice) |
 Myleene KlassDr. Holzwurm (voice) | Dr. Holzwurm (voice) |
| RRobin WalshDr. Holzwurm's Igor (voice) | Dr. Holzwurm's Igor (voice) |
| MMatt McKennaDr. Herzschlag (voice) | Dr. Herzschlag (voice) |
 John CleeseDr. Glickenstein (voice) | Dr. Glickenstein (voice) |
 Steve BuscemiScamper (voice) | Scamper (voice) |
 Sean HayesBrain (voice) | Brain (voice) |
 Suzy Eddie IzzardDr. Schadenfreude (voice) | Dr. Schadenfreude (voice) |
 Jay LenoKing Malbert (voice) | King Malbert (voice) |
 Jennifer CoolidgeJaclyn / Heidi (voice) | Jaclyn / Heidi (voice) |
 Molly ShannonEva (voice) | Eva (voice) |
 James LiptonHimself | Himself |
 Christian SlaterDr. Schadenfreude's Igor (voice) | Dr. Schadenfreude's Igor (voice) |
 Arsenio HallCarl Cristall (voice) | Carl Cristall (voice) |
 Jess HarnellAnnouncer / Royal Guard #2 (voice) | Announcer / Royal Guard #2 (voice) |
| ZZoë BrightBlind Woman / Killiseum Fan #1 (voice) | Blind Woman / Killiseum Fan #1 (voice) |
| SSophia EraklisBlind Orphan #1 (voice) | Blind Orphan #1 (voice) |
| AA. Cheron HallBlind Orphan #2 / Blind Orphan #4 (voice) | Blind Orphan #2 / Blind Orphan #4 (voice) |
| AAlexander LeondisBlind Orphan #3 (voice) | Blind Orphan #3 (voice) |
| MMichael LeondisBlind Orphan #6 (voice) | Blind Orphan #6 (voice) |
| NNicole LeondisBlind Orphan #7 (voice) | Blind Orphan #7 (voice) |
| JJuliana LeondisBlind Orphan #5 (voice) | Blind Orphan #5 (voice) |
| RRobin TisserandBlind Orphan #8 (voice) | Blind Orphan #8 (voice) |
 Paul VogtBuzz Offmann (voice) | Buzz Offmann (voice) |
 Frank WelkerAnimals' vocal effects (voice) (uncredited) | Animals' vocal effects (voice) (uncredited) |
