One Hysterical Night(1929)

The scheming aunt and uncle of William Judd, heir to the family fortune, persuade him to pose as Napoleon at a fancy masquerade ball, but they are actually having him committed to an insane asylum. Since all the other inmates/attendees think they are historical figures such as Robin Hood, the Duke of Wellington, Paul Revere, William Tell, Salome, Robinson Crusoe, Sherlock Holmes and others, it takes a while for Judd to separate the wheat from the chaff and prove he is not deranged. His quest becomes more urgent when he falls in love with a nurse named Josephine, who does not think she is Napoleon's "Josephine" but is convinced Judd thinks he is Napoleaon.