Rent Night Patrol (1984)

Melvin (Murray Langston) has a problem. As a rooking cop, he ranks among the best... of the worst. Inept, hapless and shy, his daily routine takes him from misadventure to misadventure. But by night the normally bungling bobby transforms into "The Unknown Comic". Disguised only with a paper bag over his head, Melvin has audiences eating out of his hand, if only the same were true of the voluptuous lady in the front row. A loony psychiatrist, a police captain who is a pathological liar, a playboy partner and the dowdy but sweet police officer Sue (Linda Blair) all add to the confusion and fun. As his duel personalities begin to cause problems, he must decide which one he's going to live with!