Features, for the last time, the redesigned overweight Elmer Fudd of the early 40s.
When Bugs puts on Elmer's Mountie hat, pretending to be a higher-up, he tears Elmer out of his articles of clothing by means of getting drummed out of the service, background drum music included. Getting "drummed out" means to be dishonorably discharged from an important occupation such as a military service.
Vitaphone production reel #629A.