Continuity mistake: After Ozma unstraps Dorothy from the pedestal, they run from the room, leaving both of the double swing-doors wide open. In the next shot of Dorothy and Ozma running down the hallway though, the left door is closed. (00:18:40)
Visible crew/equipment: When Billina and Dorothy are stuck in the crate, when Billina says "how's my grammar," you can see a wooden board has been nailed to the crate to cover up the spaces in between the bars, so that the puppeteer can crouch down and control Billina. (00:23:00)
Visible crew/equipment: After just meeting Tik-Tok, Dorothy winds him up, and then he bows, and raises his hat. As he bows a crewmember can clearly be seen crouched behind him. (00:36:20)
Visible crew/equipment: When Tik Tok is spinning around and hitting the Wheelers with the lunch pail, a camera and crewmember are reflected in the shiny copper of Tik Tok's front. (00:37:50)
Audio problem: When Tik Tok lets the Wheeler go, as the Wheeler skates off he is laughing and saying "Behave." His mouth is clearly out of sync with the audio, however. (00:39:15)
Visible crew/equipment: When Mombi leads Dorothy into the 'head' room, as the camera moves along a crewmember in a pink shirt, wearing glasses, is reflected in the glass screens of the head cases. (00:41:40)
Visible crew/equipment: As the camera is panning around to show off the variety of heads Mombi has collected, in one shot you can see the reflection of the cameraman with a camera in one of the glass screens. (00:41:50)
Continuity mistake: When Dorothy looks up and spots the head of the 'Gump' on the wall, it is covered with cobwebs. Later when Jack removes it for the couch, it is clean. (00:48:20 - 00:50:50)
Visible crew/equipment: When Dorothy is opening the mirrored door to Mombi's bedroom, as she pulls the door open, a crewmember in jeans and a white tee-shirt is momentarily reflected in it. (00:50:10)
Visible crew/equipment: When Billina lands on the couch with the cord, as she flies down some mechanism controlling her can be seen, attached to her feet and legs. (00:50:50)
Continuity mistake: When Dorothy unties the red key from Mombi's wrist, while she is asleep, Mombi then snores and rolls over, and the red key lays on the bed. The position of the black ribbons attached to the key repeatedly changes between subsequent shots. (00:51:20)
Visible crew/equipment: When Jack's head falls off, it is flying in the air, near the couch. Two black wires holding it up are visible. (01:01:25)
Visible crew/equipment: Wires are clearly visible attached to Dorothy's shoulders, Jack Pumpkinhead's pumpkin head and his body, as everyone falls down from the sky after the couch goes bonkers. (01:02:05)
Visible crew/equipment: When Dorothy falls down into the Nome Kings lair, she falls to the floor and slides along into the scarecrow. The black sled she is sliding on is momentarily visible as she passes the camera. (01:07:05)
Visible crew/equipment: When the Nome King says "I know something which will cheer you up," it cuts to Jack Pumpkinhead and Tik Tok sliding along the ground. The track which is sliding them along is visible. (01:08:55)
Continuity mistake: When the Wheelers have arrived back to Mombi's castle, in one shot you can see a broken pillar next to one Wheeler, totally bare. In the next overhead shot a long vine of ivy is laying on it. (01:09:20)
Visible crew/equipment: When Dorothy, Tik Tok and Jack are eating and drinking in the Nome King's lair, Tik Tok says "What is it we are risking?", and there is a small explosion, causing the table to fall, and them to all fall back. A wire attached to the table to make it fall is visible to the right of the screen. (01:11:50)
Visible crew/equipment: When Dorothy first enters the room full of ornaments, the camera pans backwards, away from her. The camera passes tables of ornaments. Watch the large blue vase to the right of the screen, and a cameraman can be seen reflected in it, walking backwards with the camera. (01:18:45)
Continuity mistake: When Dorothy finds the small green glass ornament, she shouts "Oz!", and the Scarecrow appears. In the shot when Dorothy calls "Oz", there are two large ornaments to the right side of the counter. Then when it cuts and the scarecrow "appears", the ornaments have now moved a few feet away, so that the Scarecrow can comfortably "appear." (01:23:55)
Visible crew/equipment: After Billina lays an egg in the Nome Kings mouth, the King drops Jack Pumpkinhead to the floor, and wires attached to him, out at the side, are visible to let him down gently. (01:28:55)
Answer: She was in the human world so she was in disguise.