Todd Phillips' The Hangover is a riotous comedy about three friends who wake up after a wild Las Vegas bachelor party with no memory of the night and a missing groom. Starring Bradley Cooper, Ed Helms and Zach Galifianakis, the film combines chaotic humor, escalating consequences and absurd misadventures, redefining modern buddy comedy and spawning a hugely successful franchise.

Från IMDB:
Three buddies wake up from a bachelor party in Las Vegas with no memory of the previous night and the bachelor missing. They must make their way around the city in order to find their friend in time for his wedding.