Other mistake: As they walk through the forest in the shot before Dorothy says, "I don't like this forest" there are some cool digital glitches in the lower left hand corner of the screen which look like a strand of blue Christmas lights blinking on and off. (Restored and re-mastered DVD version only).
Continuity mistake: In the beginning of the movie Miss Gulch parks her bike on the fence in front of the Gale's house and it's obvious that the fence continues in the same direction past the gate. When Dorothy comes back during the storm the fence now curves around right after the gate.
00:08:15 - 00:15:25????
Continuity mistake: As they enter the scene with the Cowardly Lion, the Scarecrow falls and then jumps over a patch of weeds growing in the middle of the Yellow Brick Road. In the next shot he does the exact same thing only about three feet behind the patch of weeds that he jumped over before.