Magical Maestro (1952, animated short)

Magical Maestro is a 1952 American animated short comedy film directed by Tex Avery and produced by Fred Quimby for Metro-Goldwyn-Mayer. It features the Great Poochini (played by Butch Dog), a canine opera singer who spurns a magician. The magician is able to replace Poochini's normal conductor prior to the show through disguise. In 1993, Magical Maestro was selected for preservation in the United States National Film Registry by the Library of Congress as being "culturally, historically, or aesthetically significant", making it the only Tex Avery cartoon so far to be inducted.

History:
The concept of cartoons with insinuating situations is hardly new — Tex Avery especially featured a few quick jokes of this nature in his cartoons. Magical Maestro, for example, shows Poochini with a male and female rabbit on each arm. He lowers his arms behind his back and when he raises them again, he now has an additional dozen baby rabbits on them, six on each arm.
This cartoon features a gimmick only seen in Tex Avery films, the "hair gag". Because cartoons were shown originally in movie theatres, the film strip, if loaded incorrectly, would rub against the gate mechanism, shaving off tiny "hairs" of celluloid. These hairs would get caught in the "gate" of the projector. Sometimes it would skitter across the projection light, resulting in a gigantic hair appearing on the movie screen. In this cartoon, the opera singer pauses mid-song to pluck the offending hair from the film and tosses it aside, one of Avery's many ways of his characters breaking the fourth wall. It wasn't the first time Avery used this gag: it was also used in Aviation Vacation (1941).
The role of Poochini is portrayed by Butch the Irish dog, a frequent star of Avery's cartoons of that era (often alongside Droopy).

Influence:
The "hair gag" would later be used by English comedian Benny Hill in the closing chase sequence of his April 25, 1984 show. As he is being chased by medical staff and an ambulance in and around a hospital area, he notices a hair moving around the bottom right corner of the screen, and at a certain point stops his pursuers long enough for him to pluck the hair out before the chase resumes.
Tom and Jerry Tales episode "Way-Off Broadway" features a gag similar to Poochini's transformations, in that Tom is forced to adapt to various pieces music when Jerry changes them on a radio.