During World War II, a junior American Army officer, Lt. Peter Stirling, gets sent to the psychiatric ward whenever he insists that an Army mule named Francis speaks to him.
| Actor | Role |
|---|---|
 Donald O'ConnorPeter Stirling | Peter Stirling |
 Patricia MedinaMaureen Gelder | Maureen Gelder |
 Zasu PittsValerie Humpert | Valerie Humpert |
 Ray CollinsColonel Hooker | Colonel Hooker |
 John McIntireGeneral Stevens | General Stevens |
 Eduard FranzColonel Plepper | Colonel Plepper |
 Howland ChamberlainMajor Nadel | Major Nadel |
| JJames ToddColonel Saunders | Colonel Saunders |
 Robert WarwickColonel Carmichael | Colonel Carmichael |
 Frank FaylenSergeant Chillingbacker | Sergeant Chillingbacker |
 Tony CurtisCaptain Jones | Captain Jones |
 Mikel ConradMajor Garber | Major Garber |
 Loren TindallMajor Richards | Major Richards |
 Charles MeredithBanker Munroe | Banker Munroe |
 Chill WillsFrancis the Talking Mule (voice) | Francis the Talking Mule (voice) |