Dr. Jäkel och Mr. Hyde

Jerry Lewis

Professor Julius F. Kelp / Buddy Love / Baby Kelp

Stella Stevens

Stella Purdy

Del Moore

Dr. Hamius R. Warfield

Henry Gibson

Gibson, College Student

Kathleen Freeman

Millie Lemmon

Richard Kiel

Man in Gym (uncredited)

Norman Alden

Football Player

Howard Morris

Mr. Elmer Kelp

Elvia Allman

Edwina Kelp

Milton Frome

Dr. M. Sheppard Leevee

Doodles Weaver

Rube

Murray Alper

Gym Attendant (uncredited)

Buddy Lester

Bartender

Med Flory

Football Player

Seymour Cassel

Bored Man

Stephanie Hill

Waitress (uncredited)