Yanky Clippers(1929)

A puppy is forced into a barber shop run by Oswald the Rabbit. Oswald can't shave the dog's back at first, as the hair keeps growing back. He eventually realizes the mutt's drinking hair tonic and so he takes the bottle away and finishes the job. A hippo's next in line, then an elephant, then a truculent and lascivious bear, all with equally humorous results.