The hilarious first installment of this trilogy which they desperately tried to recreate the second and third time. For those that may have somehow never seen it, it's basically about one hell of a stag party that goes dramatically, and pretty damn hilariously wrong. It launched the career of Zach Galifianakis, who's character was responsible for a hell of a lot of bearded men's Halloween costumes there for a while, and pretty much served as the marker for great movie comedies since.