Continuity mistake: When Roy plunges into the water, there should be pieces of rope around the bottom of the pulley device he is hanging from, but there is none.
Continuity mistake: In the beginning, Lin Wang goes from holding the puzzle box in one shot to holding her father's hand in another shot.
Continuity mistake: In the final fight, we see Rathbone flip his sword at one point so he is holding it "properly", but in the previous cut he was already holding it in the right way. This is because much of the fight was cut in editing, and several pieces of sword fighting were taken out.
Deliberate mistake: When Roy plunges into the water, it is pretty obvious he is a dummy.
Continuity mistake: When John is trying to lift Roy out of the water it seems to take a full rotation of the turnstile to raise him up a foot above the water, but when John is fighting with the guard he moves the turnstile back and forth about 2-3 feet each way and you see Roy dipping in the water and raising out about a foot above the water then back in and out of the water.
Continuity mistake: During the climatic fight scene between Jackie and the baddie in the Clock Tower, the background was the inner side of the clock. There was silhouette of the clock's hand without Owen on it when Jackie was dueling the villain on the platform. However, when Jackie and the villain crashed through the same clock face, Owen was hanging on the clock's hand. (01:33:30)
Factual error: When Chan and Wilson hitchhike, they stick out their thumbs to catch a ride from a buggy. Hitchhiking in this way wasn't popular until the 1930's; the movie is set in the 1880's.
Continuity mistake: At the end of the library fight scene, a guard is trapped in a rung on a ladder, leant backwards against the bookcase (so the guard is "on his back", head facing the books). Between shots, the amount of his body trapped in the rung changes, going from his shoulders, to most of his arms. It keeps changing between shots.
Continuity mistake: In the fight scene in the library, Chon throws a small book at the guard. When the guard cuts it using his sword, the pages that were/are in it are big and white.
Factual error: Near the start, we see a long shot of New York Harbor, where we can see the Statue of Liberty under construction. When we see the statue it's green, which comes from the statue corroding, which it hasn't had time to do.
Factual error: In the scene where Owen Wilson and Jackie Chan confront the street urchin who stole Wilson's watch, Wilson tells him they have "parents who love us", but as he says it he is looking over way over the boy's head. [If you watch the outtakes, Owen Wilson says he feels "so mean" talking to a child that way, so it's possible he simply couldn't be that mean to a child while looking him in the eye. Or he could have been trying to keep from laughing. Either way, it's still a valid mistake, this is just a possible explanation.]
Continuity mistake: Towards the middle of the movie Wilson is sitting down with some wine beside him on the table talking to Chan. In the first shot the glass is almost full, in the next shot it is nearly empty and has moved, and in the next shot it is once again almost full.
Factual error: During the scene when they are about to try to drown Jackie & Owen you can see the ceiling. On it are large shop lights. Even though lights were invented over 50 years beforehand, lights that new looking and of that kind were not.