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.
Factual error: Towards the beginning of the film, when Kitchener is shown inspecting Harry's old regiment, one of the African or Egyptian troops is shown to be wearing the Pattern 1914 Infantry Equipment, not made until 1914 at the earliest. Additionally, it has the 1918 modification to have two closing straps, so is over 20 years too late for the 1894 date at that point.