Vince Vaughn and Owen Wilson came up with most of the wedding crashing rules
Among the more memorable parts of Wedding Crashers is the list of rules that the characters of Vaughn and Wilson quote throughout the movie (I’ll manage to have a poster of the rules in my dormitory). However, these rules were not passed on by either Chazz Reinhold or the screenwriters.
In the 15th anniversary retrospectives in Variety and Mel Magazine, Dobkin, Vaughn and Wilson say they worked actively together to finalize the script, written by Steve Faber and Bob Fishers. In a separate interview with IGN, the two stars revealed that it included most of the rules for crashing weddings.
According to the stars, there were only about two rules in the original script, but when they worked on a scene with a little improvisation, they often created new rules to suit their banter.
When it comes to following the rules, Wilson says that whenever he’s at a wedding, he tries to follow rule # 17: “Get involved by making yourself stand out.”