Continuity mistake: When the six main characters are watching the movie on how to play dodgeball, a young Patches messes the little boy's hair, leaving it sticking up in the back and mildly flat in the front. In the very next shot, the little boy's hair is neat and all flat. (00:23:50)
Continuity mistake: During the tournament when it's just Gordon versus the entire other team, the background advertisements change multiple times. The problem is, they appear to be hung there, not electronic.
Other mistake: Peter took the $100,000 bribe White gave him and turned it into $5,000,000 by betting on his team. He did this, so he could buy enough shares of Global Gym stock and take over the company, and in the process kick out White as the CEO. The problem is $5 million wouldn't be near enough to gain control of the company, to be public its value would have to be at least in the tens of millions.
Answer: There were many celebrity cameos throughout the film. It's just kind of strange that Chuck Norris would do this.