Continuity mistake: In the scene where Jonathan picks up the scarab, it breaks open and the beetle inside starts to crawl under his skin. We see Brendan Fraser tear Jonathan's shirt and cut the beetle out of him. However, in the very next scene, we see Jonathan walking into the temple, his shirt is intact and there is no blood to be seen. (01:37:05 - 01:38:30)
Factual error: The priest says that St. John saw the number 666 in his vision, but it was actually 999 inverted. I'm not sure, but I don't believe St. John read modern Arabic numerals like we do. Didn't he read Roman numerals? I think if St. John saw the number 666, it would actually be DCLXVI. (01:05:40)
Continuity mistake: In the flashback to the death of the headless horseman, when the horseman's steed gets shot and falls to the ground, the blood and the wound are on the right side of the horse...later in the scene when the horse is seen again, the wound is on the left side of the horse. (00:16:45)
Audio problem: After the part where Johnny Depp finds his bookstore friend dead, he gets back in the cab. After driving for a while, he tells the cab driver to pull over to the phone booth. The cab driver says "No problem, sir" but you can see the cab driver's lips in the rear view mirror, and they never move.
Revealing mistake: When Claire jumps down into the silo filled with apples, the whole top layer of apples bounces, which indicates that there is only a thin layer of apples instead of apples all of the way down. Soft material would have been under the apples during filming. Rotting apples wouldn't have that sort of give normally.
Continuity mistake: When singing the song about what they would do if the monster came to their room in the night, Simon puts on Alvin's duvet/blanket as a cape. It then shows an imagination sequence where the blanket is a correctly sized cape to fit him. When it returns to the real world, the 'cape' is the size of his imaginary cape, nowhere near the size of the bed.Dan Moat