(CNN) -- Anyone who has ever experienced a hangover will recognize the symptoms: nausea, fatigue, a throbbing headache and pangs of regret. That's the experience of "The Hangover Part II" in a nutshell.
If the first film came as a pleasant surprise or even an invigorating shock, the only thing unexpected about the sequel is just how spectacularly stale and unfunny it manages to be.
Reassembling the same cast under the same director (Todd Phillips, who is also one of three credited screenwriters), and rehashing the clever flashback structure that worked such a treat in Vegas, "Part II" tries to disguise its diminished imagination with a radical change in scenery.
This time the guys come to in Bangkok, "Thighland," as Alan (Zach Galifianakis) keeps pronouncing it. But where the original pulled multiple metaphorical rabbits out of its cocked hat, this one soon falls into empty repetition. Actually, not so soon -- it takes a terminally dull 30 minutes to get to the wake-up scene we all know is coming.
Instead of a baby and a broken tooth, the morning after brings a monkey and a facial tattoo. It's not the groom who's missing, but the bride's 16-year-old brother. And Alan doesn't drug the alcohol this time, he ... well, see for yourself if you really want to, but you get the idea: a rare original scenario has inspired a sickly pale imitation.
(It's worth noting that the two original screenwriters, John Lucas and Scott Moore, have nothing to do with this retread.)
As a fan of "Bridesmaids" and the "Jackass" crew, I'm no prude. Comedy has license to test taboos -- just so long as we're laughing.
Scenes of a wounded monkey smoking cigarettes and pre-teen kids snorting coke and carousing with prostitutes are meant to provoke, but more than anything, they come off as desperate and rather sad.
An encounter with a Thai "lady boy" at least mitigates some of the homophobic impulses that marred the last outing, but the movie's lazy disinterest in its Asian setting carries its own sour chauvinism. We never do find out why one street brawl erupts into a riot, but you can be quite sure it has nothing to do with the anti-government protests that ignited this city not so long ago.
The male bonding that underpinned the "wolf pack" doesn't begin to justify the characters' dubious decisions this time round.
Alan, especially, seems to belong in a padded cell somewhere, though Galifianakis' comic digressions are fractionally preferable to Helms' hamming and Bradley Cooper's palpable lack of engagement. As for the ending, it makes no emotional sense at all -- and that's before someone invites Iron Mike to sing.
"The Hangover Part II" may not be the worst film ever made, but it surely ranks among the sorriest sequels. Maybe Mel Gibson's luck has finally turned.