Continuity mistake: When Alice shrinks after being huge in the forest, you can see both pieces of mushroom in her hands, untouched, although she has taken a bite out of both pieces. (00:36:40)
Continuity mistake: During the final dance number, Vera-Ellen's skirt alternates repeatedly between long and flowing and short and tight - perhaps to facilitate some of the dance moves.
Continuity mistake: When Jerry gets in Milo's car so that she can get cash to pay him for his paintings, they get into a dark green car. In the next shot they get out of a light (slightly greenish) blue car. (00:23:00)