This often hilarious movie starts off as a nasty, immoral comic romp, serving up some of the best R-rated humor since Old School. As it progresses, it gets a little afraid of itself and degenerates into your typical guy-gets-girl story. But, before it falters, the movie generates some pretty funny, sick comedy. Jeremy and John (Vince Vaughn and Owen Wilson) are a couple of major assholes. They spend wedding season crashing nuptials, lying about their identities and having sex with countless women—qualifying themselves as supreme letches. When John (Wilson) falls for a luminescent bridesmaid (Rachel McAdams), he breaks the wedding-crasher rules and begins a risky pursuit. Thanks to a cameo by a big-name star whose name I won’t reveal here, and to Vaughn being so riotously funny, the movie’s sub-par, sappy finale is tolerable. See it for the Vaughn-Wilson comedic chemistry.