Continuity mistake: When Dorothy slaps Lion on the nose for chasing Toto and shouts, "Shame on you!" in the wide shot, we see Dorothy's right arm with no mark on her skin. It then cuts to the medium shots, and there's an inexplicable long, thin blue mark (it's not a loose thread) on Dorothy's arm near her elbow, while she's holding Toto. This blue mark vanishes in the wide shot when she puts Toto down, and Lion begins to sing. (00:50:25)
Continuity mistake: During the Blue Birds in the Moonlight song you can see Gulliver holding his drink. In the next shot while he's laughing the drink has disappeared.
Continuity mistake: When Daffy gives Casper a card, he is seen holding the card with his fingers in the middle, but when we see a close-up of the card in the next shot, Casper's fingers are now at the top of it.
Continuity mistake: When the dog in the audience has his feet crushed by the hippopotamus sitting down on his chair, you can see that there is an empty chair next to the dog, but in the next shot the chair has disappeared.