Continuity mistake: Dorothy raises her right arm and points at the horizon and cries, "There's Emerald City!", then lowers her arm. A shot later from the angle shot from behind, it's raised again and she's repeating all previous movements. (00:54:41)
Continuity mistake: When Toto escapes from the castle, jumping over the moat, Dorothy starts crying. A shot later, her right arm is leaning on the wall. (01:17:46)
Continuity mistake: When Dorothy wakes up in Kansas, Prof. Marvel sneaks up in the window behind. Dorothy's pigtails change positions between shots.
Revealing mistake: When Dorothy bumps into the Tin Man, she knocks on his foot, which sounds metallic. However, her fist sinks, revealing it is made of a soft material.
Visible crew/equipment: While Dorothy and the other characters are cornered in the Wicked Witch's castle, when Dorothy grabs the bucket of water and tosses it at Scarecrow's arm, the water hits the Witch. In the closeup of the Witch's face, you can see a crew member's hand (a long sleeve can be seen at the wrist) in the upper left side of the shot. (01:26:20)
Other mistake: When Dorothy's house is falling back to Kansas, just before it lands, there is about a 1 or 2 second shot of what looks like production notes written in blue ink.
Suggested correction: There are no production notes visible anywhere.
Revealing mistake: When they meet the Wizard for the first time, his big projected head doesn't reflect off the shiny floor, like everything else. (01:09:54)
Factual error: Tin doesn't rust.
Visible crew/equipment: When the gang runs into the guard at the door, they all walk to the right of the screen to talk to him. While they're walking, you can see the shadow of the boom mic following them.
Revealing mistake: During some scenes, straw-stuffed Scarecrow's pant legs and his boots would sometimes have a gap that reveals the skin of Ray Bolger's leg. Two examples are, at Emerald City when Scarecrow places Lion's "cape" on him, and also when Dorothy and her friends are told the Wizard says to go away. (01:05:50 - 01:07:25)
Continuity mistake: When Professor Marvel guesses why Dorothy is running away, she's holding her suitcase with the lid facing Marvel. But in Toto's closeup, as he snatches the hotdog from Marvel's long grill fork, the suitcase is turned the opposite way with its lid facing Dorothy. Then it changes back, so the suitcase lid faces Marvel again. (00:12:10)
Continuity mistake: After Zeke rescues Dorothy from the crowded pig pen, Hickory wipes his face and neck with the rag in his right hand, but then it cuts to another angle, and the rag is suddenly in his left hand. (00:04:20)
Continuity mistake: When Dorothy slaps Lion on the nose for chasing Toto and shouts, "Shame on you!" in the wide shot, we see Dorothy's right arm with no mark on her skin. It then cuts to the medium shots, and there's an inexplicable long, thin blue mark (it's not a loose thread) on Dorothy's arm near her elbow, while she's holding Toto. This blue mark vanishes in the wide shot when she puts Toto down, and Lion begins to sing. (00:50:25)
Continuity mistake: While Dorothy, Tin Man, and Scarecrow are walking in the dark and creepy forest, just as Dorothy begins to sing "Lions and Tigers and Bears" in the medium shot, Tin Man is holding up the axe in his left hand. But it cuts to the long shot, and the axe is in Tin Man's right hand between shots. (00:48:40)
Revealing mistake: The moment before the Wicked Witch picks up the red hourglass to throw at Dorothy n friends, the flying monkey next to her is suddenly a miniature or reduced in size.
Continuity mistake: During the tornado scene, Dorothy gets knocked out by the windows, but right before the house hits the ground, the windows are back and intact.
Continuity mistake: When the Wicked Witch leans down to see the ruby slippers sticking out from under the house, she is pointing down at them, and practically touches them. But in the subsequent shots, she is in her standing spot from prior, pointing between Dorothy and the house.
Continuity mistake: When the Tin Man tells Dorothy that he was chopping that tree, she starts to turn her head to look at the tree. But then in the jump cut closer, suddenly she's looking back at the Tin Man.
Continuity mistake: When the witch is making her way towards the house a shadow disappears and reappears.
Other mistake: When the witch approaches Dorothy and Glinda, her legs are white, not green.