Continuity mistake: When the guy has his whole leg cut off when they are talking about the tiny net, nobody is sitting right by him, but when it shows his leg, you see other legs right by him.
Continuity mistake: Sometimes the back of the Chosen One is shown, and you can tell it's the guy from the last movie.
Revealing mistake: When the Chosen One fights Betty in the water he gets knocked down. When he gets up you can see that it's not Steve Odenkerk but the guy who was in the original kung-fu movie they added people and audio to.
Answer: Some scenes/shots were taken from the old movie, while others were made specifically for this movie. Additionally, numerous shots were "composited" to place new characters in the old footage.