 Jerry LewisProfessor Julius F. Kelp / Buddy Love / Baby Kelp | Professor Julius F. Kelp / Buddy Love / Baby Kelp |
 Stella StevensStella Purdy | Stella Purdy |
 Del MooreDr. Hamius R. Warfield | Dr. Hamius R. Warfield |
 Henry GibsonGibson, College Student | Gibson, College Student |
 Kathleen FreemanMillie Lemmon | Millie Lemmon |
 Richard KielMan in Gym (uncredited) | Man in Gym (uncredited) |
 Norman AldenFootball Player | Football Player |
 Howard MorrisMr. Elmer Kelp | Mr. Elmer Kelp |
 Elvia AllmanEdwina Kelp | Edwina Kelp |
 Milton FromeDr. M. Sheppard Leevee | Dr. M. Sheppard Leevee |
 Doodles WeaverRube | Rube |
 Murray AlperGym Attendant (uncredited) | Gym Attendant (uncredited) |
 Buddy LesterBartender | Bartender |
 Med FloryFootball Player | Football Player |
 Seymour CasselBored Man | Bored Man |
 Stephanie HillWaitress (uncredited) | Waitress (uncredited) |
 Marvin KaplanEnglish Student | English Student |
 Skip WardFootball Player | Football Player |
 Billy BletcherPlumber (uncredited) | Plumber (uncredited) |
 Robert DonnerCollege Student (uncredited) | College Student (uncredited) |
 Art GilmoreNarrator (voice) (uncredited) | Narrator (voice) (uncredited) |
 William EngesserMan In Gym | Man In Gym |
