Chris Rock

Osmosis Jones (voice)

Laurence Fishburne

Thrax (voice)

David Hyde Pierce

Drix (voice)

Brandy Norwood

Leah (voice)

Elena Franklin

Shane Detorre

Bill Murray

Frank Detorre

William Shatner

Mayor Phlegmming (voice)

Ron Howard

Tom Colonic (voice)

Kid Rock

Kidney Rock (voice)

Molly Shannon

Mrs. Boyd

Chris Elliott

Bob

Jonathan Adams

Officer Tom (voice)

Carlos Alazraqui

Spanish Germ (voice)

Keith Anthony

Additional Character Voices (voice)

Eddie Barth

Conductor (voice)

Sally Brooks

Additional Character Voices (voice)

Rodger Bumpass

Joe Cramp / Announcer for Nerve News Network (voice)

Michael Carven

Additional Character Voices (voice)

Paul Christie

Dan Matter / Germ (voice)

Janis Dardaris

Additional Character Voices (voice)

Wendy Dillon

Additional Character Voices (voice)

Antonio Fargas

Chill the Flu Shot (voice)

Eddie Frierson

Frank Police Department Officer (voice)

Donald Fullilove

Doughnut (voice)

Jackie Gonneau

Additional Character Voices (voice)

Shannon Gregory

Additional Character Voices (voice)

Richard Steven Horvitz

Additional Character Voices (voice)

Rif Hutton

Charlie (voice)

Art Kimbro

Additional Character Voices (voice)

Joyce Kurtz

Additional Character Voices (voice)

Anne Lockhart

Female Red Blood Cell (voice)

Sherry Lynn

Trudy (voice)

Danny Mann

Musician Cell (voice)

Mickie McGowan

Brain Librarian (voice)

Kenny Olson

Kidney Rock Band (voice)

Jason Krause

Kidney Rock Band (voice)

Joe C.

Kidney Rock Band (voice)

Stefanie Eulinberg

Kidney Rock Band (voice)

Jimmie Bones

Kidney Rock Band (voice)

Uncle Kracker

Kidney Rock Band (voice)