Revealing mistake: Towards the end of the movie, the principal puts on his hat which turns his hair green. But you can see the green paint has already been applied before he puts his hat on.
Revealing mistake: When Branch first takes Poppy into his bunker, and down into his storeroom, the lever that he uses isn't there, but when the shot goes to Poppy, and then returns to Branch, the lever is magically there.
Revealing mistake: When Sera is explaining to Yugi why she gave him the puzzle piece, in the shot where she says "He's giving in to fear and anger," Yugi is supposed to be looking at her, but his eyes do not appear to be aligned with her face. He is looking straight forwards instead of downwards. (01:12:55)