Charlie McCarthy, Detective (1939).

Edgar Bergen, Constance Moore, and Charlie McCarthy
in Charlie McCarthy, Detective

In the comic Charlie McCarthy, Detective, Charlie McCarthy, Mortimer Snerd, and Edgar Bergen are on the case when shady magazine publisher Louis Calhern is murdered. Robert Cummings costars. Charlie sings, "I'm Charlie McCarthy, Detective . . . they call me the Slap-Happy Sleuth." Despite Charlie's assertions, it's Edgar who does most of the detecting in the film.