Jason Lee as Shoeshine / Underdog (voice)

Jim Belushi as Dan Unger

Patrick Warburton as Cad

John Slattery as Mayor

Peter Dinklage as Dr. Simon Barsinister

Brad Garrett as Riff Raff (voice)

Taylor Momsen as Molly

Amy Adams as Polly Purebred (voice)

Alex Neuberger as Jack Unger

Larry Vigus as Security Guard

Bates Wilder as Cop

Frank Ridley as Police Sergeant

Alexander 'Alex' Garde as Small Boy

Diana Shneider as Police Secretary

Samantha Bee as Principal

John Franchi as Observer

Ezra Buzzington as Referee

Jay Leno as Jay Leno

Susie Castillo as Diana Flores

Phil Morris as Supershep 1 (voice)

Michael Massee as Supershep 2 (voice)

Cam Clarke as Little Brown Dog / Supershep 3 (voice)

John DiMaggio as Bulldog / Supershep 4 (voice)

Danny Mastrogiorgio as Crazy Dog (voice)

Jess Harnell as Astronaut (voice)

Susan Garfield as Office Worker

Timothy Crowe as Police Chief