Continuity mistake: A couple of scenes after the baker's wife ripped off most of Rapunzel's hair, it has grown back to full length so that the prince can climb up to the tower on it.
Continuity mistake: While Annie and Stacks are in the Stacks Mobile helicopter, Annie's seatbelt shoulder strap repeatedly changes from being over her shoulder properly to being under her arm. (01:03:00)
Continuity mistake: When Larry and Nick Daley first enter the British Museum, Nick takes his beanie off twice, in consecutive shots.
Continuity mistake: When the family turn off the museum electrical system and then run away, their shoes are dry and do not leave wet footprints on the floor. Only when Millicent checks the electrics do the footprints appear.
Continuity mistake: Just before seeing Principle Celestia, and they are walking down the hallway, the cutie mark on Sunset's shirt disappears.
Continuity mistake: When Alexander wakes up to find his brother, Anthony, still asleep, Anthony has no zit on his face. When he looks into the mirror about two minutes later, there is an existing zit on his face, and he has to put a Band-Aid on it.
Continuity mistake: At the end of the movie when the three kids are on the stage, in the first shot Jason Jones stands on the left side of the stage, Dylan in in the middle and the Kimi on the right side. But in the second shot, Jason stands on the right and the Kimi on the left. (00:21:20)
Continuity mistake: During the "Perfect Puppy" silly song, Bob places a newspaper he had been reading on the couch beside him when Larry starts singing. When Bob shows Larry the picture of the dalmatian, the newspaper has vanished. When the shot cuts back to Bob, the newspaper has returned. (00:16:55)
Continuity mistake: The dog the boys were trying to catch was facing the fence with his nose very close to it. After one of the boys threw a blanket (or piece of material) over the dog, the dog was facing them instead of the fence. Also, the dog was not as close to the fence and the background didn't appear to be the same. (00:06:07)
Continuity mistake: When Thomas first arrives at the Clay Pits, Timothy can be seen with a train of trucks. In the next scene, they have disappeared.