Jason Lee as Dave

David Cross as Ian

Cameron Richardson as Claire

Jane Lynch as Gail

Justin Long as Alvin (voice)

Matthew Gray Gubler as Simon (voice)

Jesse McCartney as Theodore (voice)

Allison Karman as Female Intern 1

Tiara Parker as Female Intern 2

Kira Verrastro as Female Intern 3

Veronica Alicino as Amy

Beth Riesgraf as Mother in Store

Adriane Lenox as Vet

Don Tiffany as Engineer

Lorne Green as Director

Kevin Symons as Ted

Frank Maharajh as Barry

Greg 'G-Spot' Siebel as Photographer

Oliver Muirhead as Butler

Jayden Lund as Security Guard

Erin Chambers as Press Coordinator

Jillian Warry Barberie as Jillian Reynolds

Chris Classic as DJ

Adam Riancho as French Doll (voice)

Axel Alba as Spanish Doll (voice)

Rosero McCoy as Choreographer

Alexis Boyd as Dancer

Criscilla Anderson as Dancer

Kevin Fisher as Dancer

Kyndra Reevey as Dancer

Tucker Barkley as Dancer

Celestina Aladekoba as Dancer

Laura Edwards as Dancer

Christopher Scott as Dancer

Miss Prissy as Dancer

Bryan Gaw as Dancer

Michelle Maniscalco as Dancer

Nick Drago as Dancer

Melanie Lewis as Dancer

Natalie Cohen as Poolside Girl (uncredited)

Ross Bagdasarian, Jr. as Alvin (singing voice) (uncredited)

Janice Karman as Theodore (singing voice) (uncredited)

Lisa Mason Lee as Band Member (uncredited)

Meghan Noone as Alvin's Fan (uncredited)

Chris Rossi as Dancer (uncredited)

Jameel Saleem as Band Roadie (uncredited)

Melanie Stephens as Dancing DJ (uncredited)