Revealing mistake: When Chosen One and Ling are talking and Chosen One says/shouts, "I implore you to reconsider", look at his head as the camera zooms in. After the zoom stops, you can see that Chosen One's head "grows" for about a half-second, the result of a flub-up of the special effects. (His face is pasted onto another actor's body.).
Revealing mistake: During the scene where Betty is at the table with the Chosen One, when the camera is behind the Chosen One, you can see a mustache on him sticking out on the side. The Chosen One does not have a mustache. This also happens when Betty is performing his skill. This is where Steve Oedekerk is replacing Master Tang instead of the Chinese guy he usually does. (00:25:35)
Continuity mistake: When Chosen sees all his friends wounded in the field, he has a tattoo saying "mouth" with an arrow on his left cheek. The tattoo can't be seen after this scene. There was a deleted scene where Chosen One was captured and tortured, one of the tortures was to tattoo an arrow that said 'mouth' on it. In another one, the "one boob" woman uses magic to erase it. Still a mistake, but there's the reason. (00:54:45 - 00:56:15)
Continuity mistake: When the Chosen One is meeting with Master Tang, in the first shot you see that Master Tang is sitting down. However when Chosen One says "and that day, I vowed to find the man who killed my family", you see Master Tang walks past the Chosen One. (00:13:20)