Continuity mistake: When Dorothy comes running into the farm at the beginning of the movie, there's a lone cow in the pen behind her and a couple of white chickens that she ends up chasing in the direction of the camera as she runs near the house. Two shots later the cow disappears and the white chickens are now in the pen.
Continuity mistake: In the scene when they discover the Wizard behind the curtain there is a change in the equipment on his wall. At first the big lit up gauge thing with the two levers above it is lit, about a minute later when the Scarecrow gets his diploma the angle has changed and the gauge thing is dark.
01:28:55 - 01:29:55????
Continuity mistake: After the talking trees throw their apples at Dorothy she walks up a small hill and finds the Tin Man. If you look behind her there's a house across the Yellow Brick Road. We just saw this exact same spot in the previous shot as they were being pelted with the apples and the house is not there.