Revealing mistake: In the close-ups of the elves during the Coronation Ball, you can see the fishing wire used to attach their wings to their backs.
Revealing mistake: Near the end of the movie, when Malcolm's partner pulls out his gun and Lester shoots him, the bullet hole in the wall appears before the bullet wound in Paul Giamatti's arm.
Revealing mistake: In Thomas' first appearance, he has no cab doors. He continues to not have cab doors throughout the movie except for a few shots.