Continuity mistake: Dorothy's Aunt hands out some food, walks with her and leaves Dorothy alone. Several meters ahead there's a cart wheel and one chicken. When the angle changes, Dorothy is standing next to the wheel, which is also facing a different position, and there's a lot of chickens around.
Continuity mistake: You see a Flying Monkey with Toto before he gets picked up. (01:15:30)
Continuity mistake: In the Wicked Witch's room, she puts Toto in Dorothy's basket which now has a lid on both sides of it. Later when the boys come to rescue her, Dorothy walks over toward the hourglass, and picks up the same basket and it now has no lids on it (like earlier in the movie). (01:17:20 - 01:23:50)
Continuity mistake: In Munchkinland, when Dorothy walks the road and everyone sings "Follow the yellow brick, follow the yellow brick road," the angle cuts and a group of Munchkins have suddenly appeared in the center of the previously empty road. Dorothy was standing on the farthest point, so they had half a second to walk 10 meters, which is impossible.
Continuity mistake: The Lollipop Guild teleports all over the scene. As Glinda departs, they are behind Dorothy. As Glinda's bubble rises, several Munchkins run to where she was and wave goodbye, green shirted Lollipop Guilder (Jerry Maren) among them. Cut to Dorothy and Jerry's still behind her. (00:32:40)