“What happens in Vegas stays in Vegas” is a pretty tired cliche… but it’s certainly applicable if, say, you’re too drunk to remember what happened in Vegas.

Such is the premise of The Hangover, in which normal guy Doug (Justin Bartha) heads to Las Vegas for a bachelor party the night before his wedding. Along for the ride are Phil (Bradley Cooper) the archetypical cocky asshole best friend character; nerdy Stu (Ed Helms) whose controlling girlfriend is led to believe that the bachelor party is a stripper-free affair in Napa Valley; and Doug’s oddball future brother-in-law Alan (Zach Galifianakis) who looks sort of like the Portland, Oregon, version of the Unabomber. The movie opens with Phil — still in Vegas, five hours before the wedding — calling Doug’s fiancee to say that Doug has gone AWOL. Right then and there, it seems like the movie will pan out to be the typical “bromance,” filled with typically predictable jokes of the crude and rude variety.

The Hangover is not for everyone and if you’re the kind of person who uses the word “cinema,” that probably means you. But the movie is hilarious and not nearly as predictable as it might appear to be on the surface. Sure, most of the humor is lowbrow, crass and occasionally offensive. And of course Doug is eventually located and married without a hitch. That’s not a spoiler so much as something that’s obvious to anyone who has ever watched a movie. What makes The Hangover fresh is the timeline. If the movie were a clock, the opening scene would be 11 p.m. The next one, a flashback to two days prior, takes place the previous midnight and the rest of the story unfolds in real time. After a Jagermeister toast on the roof of Caesars Palace, the guys wake up hung-over in a trashed hotel suite. Their questions are the same as ours: Why is there a live tiger in the bathroom? Also, whose baby is that? Doug is missing and the guys go about finding him by attempting to retrace their steps, starting with a mysterious hospital bracelet.

The audience learns just what happened last night along with the characters as they find themselves on a series of misadventures, each one crazier than the last. What makes The Hangover so funny and unpredictable is that the situations are so random and ridiculous. Sure, it’s probably against the law for a comedy set in Las Vegas not to include an ill-advised wedding. But only Nostradamus and Miss Cleo would have seen some of the other gags coming.

Most movies come down to what happens at the end but in The Hangover, it’s all about the middle. To elaborate would give too much away, so let’s just say that Mike Tyson is somehow involved and that you’ve probably never found something quite like that in the trunk of your car.

Starring: Bradley Cooper, Ed Helms, Zach Galifianakis, Justin Bartha, Heather Graham, Sasha Barrase

Director: Todd Philips

Runtime: 100 Minutes

Distributor: Warner Bros

Rating: R