Du Barry was a Lady (1943)

Hat check man Louis Blore is in love with nightclub star May Daly. May, however, is in love with a poor dancer but wants to marry for money. When Louis wins the Irish Sweepstakes, he asks May to marry him and she accepts even though she doesn't love him. Soon after, Louis has an accident and gets knocked on the head, where he dreams that he's King Louis XV pursuing the infamous Madame Du Barry.