In the scene where Rabbit is stuffed in a locker covered in shaving creme, he is actually covered in menthol shaving creme. The crew was unaware that menthol burns your skin if left on too long, so after the scene, Erik Stolhanske was sent next door to a firehouse to get hosed off.
In the scene where Ursula hits Foster in the head with a snowcone, there is a set-up to indicate that the snowcone is solid. There was a mid-scene switch scheduled in which the hard snowcone would be replaced with a softer one. However, the switch did not occur during several of the takes and hence, Paul Soter took a solid block of ice to the head about nine times before they got it right.
In the syrup-chugging scene in the diner, the first few takes were done with the actors drinking thick iced tea from syrup containers, but the iced tea didn't look realistic enough. Real syrup was brought in, and the actors then did several takes in which they actually chugged entire bottles of syrup. These are the takes you see in the close-ups, however, some wide shots with the iced tea were kept in.
In the first scene that was filmed with Brian Cox (the scene on his porch, where he is reading the letter from the governor), the letter was supposed to have the lines typed out on them. Broken Lizard didn't know that when they started the scene, so they typed the lines up quickly and gave it back to him. If you look closely you can see some white out marks from what the letter originally said.
The trivia items below may give away important plot points.
In the scene cuts during the award ceremony for the state police's drug bust where Farva continuously vomits into a toilet, it was actually Kevin Heffernan vomiting. This process can be seen in the outtake reel on the DVD.