 Jason LeeShoeshine / Underdog (voice) | Shoeshine / Underdog (voice) |
 Peter DinklageDr. Simon Barsinister | Dr. Simon Barsinister |
 Jim BelushiDan Unger | Dan Unger |
 Patrick WarburtonCad | Cad |
 Alex NeubergerJack Unger | Jack Unger |
 Taylor MomsenMolly | Molly |
 John SlatteryMayor | Mayor |
 Amy AdamsPolly Purebred (voice) | Polly Purebred (voice) |
 Brad GarrettRiff Raff (voice) | Riff Raff (voice) |
 Samantha BeePrincipal | Principal |
| TTimothy CrowePolice Chief | Police Chief |
 Larry VigusSecurity Guard | Security Guard |
| MMario MarianiPolice Officer | Police Officer |
 Bates WilderCop | Cop |
| AAlexander 'Alex' GardeSmall Boy | Small Boy |
| CChristopher Francis ByrnesMailman (as Christopher Byrnes) | Mailman (as Christopher Byrnes) |
| JJoe SirianiNews Stand Guy (as Joseph Siriani) | News Stand Guy (as Joseph Siriani) |
 Sujoy DeOffice Worker #1 | Office Worker #1 |
 Michele ProudeOffice Worker #2 | Office Worker #2 |
| AAlbert M. ChanGeek Worker | Geek Worker |
| JJon PierceHot Dog Vendor | Hot Dog Vendor |
 Susie CastilloDiana Flores | Diana Flores |
| BBob JaffeProfessor | Professor |
 Bruce-Robert SerafinCity Worker (as Bruce Serafin) | City Worker (as Bruce Serafin) |
 Lonnie FarmerPasserby | Passerby |
 Anthony EstrellaMale School Teacher (as Tony Estrella) | Male School Teacher (as Tony Estrella) |
| MMalik McMullenBomb Squad Officer | Bomb Squad Officer |
| AAaron DorseyLittle Boy | Little Boy |
| WWalter CovellOld Man | Old Man |
| KKate LohmanHousewife | Housewife |
