Starring Bradley Cooper and Ed Helms. Rated 18A. Opens Friday, June 5, at the Cinemark Tinseltown

Plenty of about-to-be-marrieds wake up after stag parties bleary from the previous night’s events. But few are as confused as The Hangover’s quartet of hapless Angelenos, who find the sun streaming in on a Las Vegas hotel suite filled with empty bottles, squawking chickens, a crying baby, and a dangerous zoo animal. Also, Bachelor Number One is nowhere to be seen.

That leaves the alpha male (Yes Man’s Bradley Cooper) to call the waiting bride and explain that her fiancé can’t come to the phone right now. The rest of the very funny film, told in roundabout fashion, is devoted to the remaining trio’s increasingly arduous steps to recover their friend, and their memories, in time for the wedding.

What they find, given different sequencing and ominous music, could play like a dark thriller. But this is really a vehicle for the comic timing of The Daily Show’s Ed Helms, as a terminally p-whipped dentist, and Zach Galifianakis, as the bride’s socially deranged brother, uninvited but along for the ride.

The briskly paced movie is much more satisfyingly original than you might expect, coming from Todd Phillips, director of Old School and the Starsky & Hutch movie, and Jon Lucas and Scott Moore, who wrote Four Christmases and The Ghosts of Girlfriends Past. They have an unfortunate inclination toward sadism (spare me the Taser scene, bro). And were the filmmakers really giving Heather Graham a break by casting her as a dumb-bunny stripper? In any case, I’m glad that Helms’s improvised piano song, commenting on the action just when you need a break from it, did not stay in Vegas.