Continuity mistake: When Dorothy, Tin Man, Scarecrow, and Lion are confronting the Wizard behind the curtain, as the Wizard tells Scarecrow that anybody can have a brain, suddenly there are a bunch of flowers (they're not Dorothy's flowers from Munchkinland) set on top of the Wizard's machine. There is no explanation, and you can't see anyone placing them there. (01:28:45 - 01:29:30)
Continuity mistake: As Dorothy balances on the pigsty Zeke feeds the pigs. The bucket he passes by on his right is smooth without any ridges on its sides and the bucket he picks up from the bench has a visible indentation about one inch below the rim. He empties the first bucket than picks up the second, which shouldn't have an indentation around it but does. (00:03:55)
Continuity mistake: When the Tin Man crowns the Lion with the broken flower pot, he places the crown over the right ear, but in the next shot the crown is over the left ear. (01:06:00)
Continuity mistake: When the group emerges from the woods and is looking at the Emerald City, from the front Toto is about ten or fifteen feet to the left, standing on a rock. It then cuts to Dorothy for just a second, and then to a shot of the group from the back, and Toto is suddenly right behind them. (00:54:35)
Continuity mistake: In the scene where the tornado is forcing everyone into the storm cellar, there is a bench lying on its side. In the next scene, when Dorothy arrives at the cellar, the bench is not only turned in an entirely different position and seems to have gotten bigger, but a wash tub has been placed in front of it.
Continuity mistake: Prior to the Wicked Witch attempting to retrieve the ruby slippers from her sister, Dorothy is seen standing in front of Glinda still holding the lollipop she was given. The camera then turns to the Wicked Witch of the West and when it turns back to Dorothy, the lollipop has disappeared.
Continuity mistake: The length of the bristles in the Witch's broom changes throughout the movie. (00:29:15 - 01:26:10)
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. (01:28:40)
Continuity mistake: Just after Dorothy takes the cruller and before singing "Over the Rainbow", as she walks along the side of the building and Aunt Em says the words, "Help us out today," notice the wagon wheel leaning against the corner of the structure. Also notice that the fence just beyond the wheel has a broken top rail. Two shots later, a paddle appears and is now leaning against the wheel, and the fence is repaired. (00:05:15)