There are rules.
You can't chew gum in school. You can't play "pull my finger" at work. You can't drive naked through a Taco Bell drive thru and order a cheesy gordita. (Even though I'm sure there were no signs.) Without rules, society would break down, the world would be plunged into utter chaos, and I don't even like your stupid cheesy gorditas anyway, you corporate fascists.
Horror movies are no different. There are certain do's and don'ts to be followed, and diehard fans of the genre know them all. (For example, teenagers who have sex in a cabin while a 6' 9" hatchet killer is on the loose may not have half a brain in their heads, but soon half a brain is all they'll have in their heads.) The familiarity found in most teen scream movies is part of their appeal, and knowing the rules is like gaining membership into an exclusive club, only without all that pesky "human interaction" and "need for hygiene."
Because of this familiarity, film makers have found new ground to till. Movies like Scream and Cabin In the Woods skirt these unwritten rules while winking knowingly at the audience who they assume is in on the joke. But there are also a few films that not only wink at the audience, they slap them on the ass and guffaw in their face.
Feast, a horror comedy from 2005, is an excellent example.
