Continuity mistake: In the beginning while Dorothy is still on the farm, she walks along the pig pen fence and then falls in. When Bert Lahr picks her up out of there her dress is perfectly clean. (00:03:45)
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 the curtain gets stuck to Ballantine's pants, at first it's stuck on his side, then in the next shot it's stuck in the middle of his back.