Black Friday: Directed by Arthur Lubin. With Boris Karloff, Bela Lugosi, Stanley Ridges, Anne Nagel. Dr. Sovac transplants the brain of a gangster into his professor friend's body to save his life, but there is a side effect that causes a dangerous split personality.
Insanely it has someone's life being saved by transplanting the brain of a bank robber into it. And entirely ignores the fact that the patient should wake up as the Bank Robber, instead having him wake up as the other person who is occasionally taken over by the Bank Robber.