Other mistake: In Sarah's room, after the close-ups of Lancelot's empty shelf space and of Sarah beginning to say, "Someone..." as she finishes, "..has been in my room again," in this wide shot, while still on her bed until she leaves her room, there is a mark across Sarah's forehead that extends to the left side her eye. It isn't in the previous or following shots. (00:06:40)
Other mistake: When Fievel And Tony reunite on the streets of New York, Tony gets a piece of cheese off of a mouse trap. Watch that piece of cheese, cause Tony throws it up in the air, and you never see it come back down. (00:33:25)