Step aside, Swingers - new Vegas classic has arrived.

One can usually gauge a film's quality and likelihood of success by the reactions from screener audiences. Comprised of critics, contest winners and otherwise lucky sons of bitches, these crucial screenings determine the initial box office push for a film. If the reception is lukewarm, the film's not likely to do very well upon release.

But if the crowd goes absolutely apeshit with laughter throughout the entire film, if they're still gasping for breath in their seats well after the black-screen credits roll, you can bet your sweet ass that the movie's a surefire win. That's exactly what happened last night at the Los Angeles screening of the new Vegas-trip comedy The Hangover, A Warner Bros. release in association with Legendary Pictures.

Put simply, this is the funniest goddamn movie you'll see all year - and possibly ever. The TV spots seem to suggest that the film consists of little more than a drunk-fest bachelor party full of tits and Mike Tyson, but The Hangover is so much more than that. 

Two days before he marries his gorgeous fiancee, Doug (Justin Bartha) heads to Las Vegas with his best buddies Phil and Stu (Bradley Cooper and Ed Helms) and his future brother-in-law Alan (Zach Galifianakis), for a blow-out bachelor party they vow to never forget - or speak of ever again. They sneak up to the Caesar's Palace roof to do a celebratory shot - and that's where it all goes to hell.

The three groomsmen wake up the next morning with pounding headaches, unable remember a thing. Their luxury hotel suite is beyond trashed, the groom is nowhere to be found, there's a baby in the closet... and a tiger in the bathroom. 

With no clue about what happened and little time to spare before their missing buddy's wedding, the trio follow an insane series of clues to figure out just what the hell happened the night before. Their hopes of finding Doug and getting him back to L.A. in time for his wedding plummet with each clue they find, however, and the plot thickens to the point of absurd hilarity.

The beat-the-clock detective story mixed with the bachelor-party-gone-wrong premise is a brilliant mix - a bit like Swingers meets Very Bad Things, but without any of the dead hookers or murderous, quadriplegic nightmares at the end - and certainly no screaming goddamn Cameron Diaz. 

Bradley Cooper is the alpha male sly fox personified as Stu, while Ed Helms plays an even more milquetoast character than his day job as Andy on "The Office." They're both classic characters in their own right - and polarize each other very well, but it's funnyman Zach Galifianakis, however, who steals the show and runs like batshit crazy with it. As Alan, Doug's soon-to-be brother-in-law, we finally see a flash of the true comedic potential as Zach steps out of his schticky Comedy Central character, shows true depth and actually manages to pull off the most hysterically awesome Rain Man impression you've ever seen - guaranteed or I'm buying your next movie ticket. And by "I," I actually mean "You," but this is no time for haggling over details.

The three friends' desperate journey to find their friend includes encounters with taser-wielding cops, angry effeminate Asian gamblers (Ken Jeong in an unforgettable performance), a perky stripper (topless Heather Graham!) and yes, Mike Tyson (mini-spoiler: it's his tiger). Throughout it all, however, Cooper, Helms and even Galifianakis find the discipline to keep from going too far over the top in this film, which enables the viewer to stay engaged the entire time - it doesn't ever become outright self-parody, although it flirts dangerously with that line. And you know what? The film is better for it.

The Hangover opens in the US on June 5, the same weekend as Will Ferrell’s much-hyped Land Of The Lost. Warner Bros. will look to emphasize The Hangover’s R-rating, hoping that audiences of previous adult-themed summer comedies – such as Wedding Crashers, Knocked Up and Superbad – will flock out in droves. Director Todd Phillips, whose track record with male-centric R-rated comedies like Old School and Road Trip puts him squarely in the league of such films, has outdone himself. The Hangover is an absolutely hysterical joyride that will leave you screaming well into the credits. My hands-down favorite movie of the year thus far.

CraveOnline's Rating: 9.5 out of 10