Dodgeball - "OSQ" Times 2
At the part before that one guy (the one that basically memorizes the dodgeball rulebook) suggests they play dodgeball, watch him take out his OSQ magazine in the background. If you watch, you'll see him take out his magazine from his bag. Then...a couple seconds later...it zooms in on him, and you see him taking the same exact issue of OSQ out of his bag.
This isn't that big of a slip up..and it's not that hard to find. I found this the first time I saw this movie.