The Milkman (1950)

Roger Bradley, son of a milk magnate, isn't allowed to work for his dad's company because of a lingering war trauma: in moments of stress he quacks like a duck. Desperate to escape from idleness, he gets a job with his father's arch-rival, sponsored by eccentric milkman Breezy Albright, and promptly falls in love with the boss' daughter. But his career as a milkman soon degenerates into slapstick.