Other mistake: When entering the Haunted Forest, the Scarecrow is carrying a pistol and a stick, the Lion has a bug sprayer and net, the Tin Man has a monkey wrench and his axe. But different scenes after that shows some items missing and then returning. I guess in the insect scene that was cut, they lost all those things but the axe.
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).
Other mistake: The Witch's castle is shown twice, the first time is in the beginning of the scene when Dorothy is held in her room, and the second time is when Toto brings the three back to rescue her. Each time the painting is almost exact, even down to the lights in the windows of the castle. The only thing that changes is the walk way up to the castle, which is entirely different each time.
Other mistake: As the Wizard is pulling his curtain closed, he says the famous, "Pay no attention to that man behind the curtain," in a loud, booming voice. But he's turned 180 degrees away from his microphone, which we see a second later needs to be right in front of his mouth to make the booming voice effect.