Revealing mistake: At Jareth's castle, in the room with the Escher stairs, Sarah sees Toby and she jumps. It's very apparent that it's a stuntwoman jumping from the ledge in the wide shot. (01:30:20)
Revealing mistake: In the Director's Cut ending when Audrey II eats Seymour, it spits out his glasses, and they land in front of the camera. They pulled this off by having a pair of glasses inside the plant's mouth that would be yanked out by a string, and another pair of glasses would be dropped in front of the camera. However, the first pair gets caught in the teeth and fall back inside the mouth, but the other pair lands on the ground anyway.
Revealing mistake: During "Never Say Never" Henri instructs Chantal to fly Fievel to immigration where he should be able to find his family. At one point during this shot, Henri's right wing casts no shadow on the Statue of Liberty - only an outline of the wing's shadow is visible. (00:23:25)