One of my all-time favorite cartoons is the 1952 MGM short "Magical Maestro" directed by the great Tex Avery and produced by Fred Quimby. The premise is simple; a canine opera singer called Poochini (the world's "Greatest Baritone") rejects the proposition of a magician (Mysto) who then wreaks havoc with his magic wand on Poochini's rendition of "Largo Al Factotum" from Rossini's "The Barber of Seville". You can see it here.
The cartoon was plagued for many years by censorship because of the Chinese and black-face stereotypes (but curiously not the equally offensive depictions of Native Hawaiians or Latinos).
While the racist stereotyping seems inexcusable today, from a clearly musical standpoint the Ink Spot pastiche is incredible and those rabbits are adorable. Also watch out for the classic "hair in the gate" gag.