Continuity mistake: In the beginning while Dorothy is still on the farm, she walks along the pig pen fence and then falls in. When Bert Lahr picks her up out of there her dress is perfectly clean. (00:03:45)
Revealing mistake: When the Lion runs out of the Wizard's room, the group disappears because it is an obvious backdrop.
Revealing mistake: When the Wicked Witch scares the Munchkins in Munchkinland, where Dorothy lands, she disappears into a cloud of smoke she creates. But you can see her sneak down into a trap door below. [As a sidenote to this entry, Margaret Hamilton was hospitalized for severe burns after a take of this shot (not the final one used) when the stage elevator got stuck and the explosion went off.] (00:30:45)
Continuity mistake: During the scene when Dorothy and Scarecrow are fighting with the trees, Scarecrow says "I'll show you how to get apples" and he gets hit by the apples. In the very next shot, a quick view of Dorothy reveals she is wearing black shoes, not her ruby slippers. (00:40:15)
Continuity mistake: During the sequence where Dorothy meets the Scarecrow, Dorothy's pigtails are first short (above her shoulders) and as the song progresses her hair gets longer (below her shoulders), then short, and then long again. (00:35:15)
Revealing mistake: Soon after Dorothy slaps the Cowardly Lion, she looks as though she is about to laugh out loud. This happens about 10 seconds or so after the slap. She even tries to put Toto in front of her face to cover up her smirking. (00:48:45)
Visible crew/equipment: When the Scarecrow says, " Did I scare you?" the camera's shadow can be seen on Dorothy's face. (00:36:00)
Revealing mistake: When the guard tells Dorothy that she may not see the Wizard, Dorothy starts crying and tells a sob story about Auntie Em. Then, it shows the guard crying, but the tears aren't coming from his eyes. They're coming from above his eyebrows. (01:08:00)
Revealing mistake: When the Lion is pulling up the Tin Man with his tail on the way to the castle, you can see a square block inside the Lion's costume to hold the tail on. (01:20:00)
Revealing mistake: During the Lion's song of, "If I only had the nerve." You can see the cameraman's shadow pass over Dorothy, the Lion, and then the log on the side of the road. Watch carefully, it comes back. (00:52:18)
Continuity mistake: When Scarecrow, Tin Man, and the Cowardly Lion are marching into the Wicked Witch's castle after taking the guards' uniforms, all three of them are shown holding the same types of spears as the guards, so when they go rescue Dorothy out of the locked room and Tin Man chops through the door with his axe, where did the axe come from? (01:22:50)
Suggested correction: I'm 63 years old and still watch The Wizard of Oz. If I remember correctly, the axe was taken off a nearby wall.
There is no scene of him taking the axe off the wall, nor is there any axe seen on any of the walls. Plus, it's the same axe he had the whole time. But the 3 also take off their coats/disguises while the camera is on Dorothy and it's possible he had the axe tucked away in the coat.
In the books, the Tin Man always has his axe and he uses it often. Perhaps it is the same in the movie.
Continuity mistake: When trying to escape the Witch's castle, the big doors close, and the gang stands in a line and starts banging on the doors. Between shots, Dorothy and the Tin Man switch sides. (01:21:15)
Continuity mistake: As the chandelier falls on the guards at the witch's castle, all the candles are blown out by the time it lands. The next shot shows some of them relit. (01:24:50)
Visible crew/equipment: Glinda sends Dorothy off saying, "Just follow the Yellow Brick Road" and Dorothy walks through the shadow of the camera's crane. (00:32:05)
Audio problem: At the very end of, "We Welcome You to Munchkin Land," at the very last 'fa la la la la laaaaaa' right before the Wicked Witch interrupts the song with her explosive arrival, you can hear someone scream before the explosion even occurs. (00:29:04)
Continuity mistake: When the Witch melts, the broom is laying several inches from her dress. In the next shot, the broom is practically touching her dress. (01:26:20)
Continuity mistake: After the Tin Man's dance, Dorothy and the Scarecrow shuffle over to a tree trunk where the Tin Man then sits. During this, the oil can in Dorothy's basket clearly falls out, but in the very next shot it is back in the basket. (00:45:25)
Continuity mistake: When the Wicked Witch scares the Scarecrow, Dorothy, and the Tin Man with fire, after the fire is thrown, not only is the Tin Man's funnel cap on backwards, everything is reversed. In order to keep the characters oriented from left to right correctly, they had to show the film from the wrong side, thus the buttons of the Scarecrow's jacket and everything else are on the wrong side. (00:46:40)
Revealing mistake: In the scene of the Haunted Forest, when Dorothy is taken away by two of the flying monkeys, you can see that as she's kicking her legs in the air that they are mechanical. The kicking is very stiff and inhuman. (01:15:30)
Revealing mistake: When everyone is still in the poppy field, after the snowstorm, Dorothy says "Look. Emerald City is closer and prettier than ever." Look behind the Lion just as Dorothy says the word "City" and you'll see that the wire attached to his tail brushes over the top of some of the poppies, knocking the snow off. (00:57:15)
