Sergeant Dead Head 1965
Directed by Norman Taurog | Starring: Frankie Avalon, Deborah Walley, Cesar Romero, Fred Clark
An astronaut goes into space with a chimpanzee. When they return to Earth after their orbit, it is discovered that the chimp has the brains of the astronaut, and the astronaut has the brains of the chimp. Complications ensue.