If one good thing comes out of The Hangover—the newest addition to Old School and Road Trip director Todd Phillips' fratboy canon—it'll be turning comedians Zach Galifianakis and Ed Helms into viable movie stars. They're both very funny guys, and here they do their best with a not-particularly-good script from the screenwriters of Ghosts of Girlfriends Past and Four Christmases. After penning those chick flicks, Jon Lucas and Scott Moore have done an about-face and written a dick flick—one that equates gross-out offensiveness with wit.

Galifianakis' awkward brand of humor dominates The Hangover, where he plays Alan, the creepy brother of a bride-to-be who tags along with the groom and groomsmen to a Vegas bachelor party. Alan slips them each a roofie, and they all wake up the next morning with no recollection of what happened. The hotel room is a mess, there's a baby in the closet, and a tiger in the bathroom. Oh, and the groom is missing.

Helms, one of the best things about The Office and The Daily Show, is sporadically funny as one of the groomsmen, a dentist named Stu. (Guess how many jokes there are with Stu the dentist claiming he's a doctor, and someone correcting him! Probably about 50.) Once they wake up, Alan and Stu—along with another groomsman, the douchebaggy Phil (Bradley Cooper, the bad guy from Wedding Crashers)—try to piece together their evening and find the missing groom somewhere in Vegas.

Alas, instead of something akin to Raoul Duke and Dr. Gonzo venturing into the seamy heart of Sin City, The Hangover comes off like an R-rated Scooby-Doo mystery. But the real problem with The Hangover is that it peaks too soon; early on, it succumbs to over-the-top ridiculousness, then keeps trying to top itself. About halfway through, it becomes repetitive, and then it just slides into monotony. The movie's offensive qualities are actually the best things about it—it's misogynistic, disgusting, nihilistic, spiteful, and stupid, but remorselessly and gleefully so—but when The Hangover can't sustain the bar it sets for itself, it eventually turns into a throbbing headache that won't go away.