1. "The Hangover Part II" is a dour, cynical rushjob of a movie that, if you enjoyed the first film (like I did), I can't recommend you avoid strongly enough. It's less a pale imitation of the original than a bizarre carbon copy of it. It's important to be clear here: This is almost exactly the same film as the first one. That sounds like something critics say about every quick-hit sequel: "It travels along similar terrain" or another fancy-foot phrase like that. But here, saying that it's almost exactly the same film as the first film is less an observation than a plot spoiler. The thought process for "The Hangover Part II" literally did not progress past, "OK, they're in Bangkok now." Except they forgot to add the jokes.
2. This time, rather than Justin Bartha getting married, it's Ed Helms, to a Thai woman whose family dislikes him because he isn't exciting enough. How little they know. The movie labors to find reasons not only to bring the gang back together -- including the film's one funny scene, in which we see what madness ensues in the bedroom of Zach Galifianakis' Alan -- but also to shoehorn our three protagonists into the precise scenario they were in last time, down to the roofies and bleary-eyed morning, the presence of Ken Jeong's Mr. Chow character, and even Mike Tyson, whose appearance makes less sense and is decidedly less amusing. There are at least four different instances in this film that one character says some variation on the line, "I can't believe this is happening again!" That might work once, self-referentially; by the fourth time, the jig is up.
3. "The Hangover" was funny, of course, but the reason it worked was because there was an actual mystery: How did these guys find themselves in this predicament? The film was almost a whodunit, a reconstruction of a backstory, little slivers of discovery that kept topping themselves, leaving enough questions unanswered that the photographs from the blackout night that played over the closing credits were not just a riot, but also a clever way to fill in the gaps we were legitimately curious about. Here, there is no mystery, no surprise, no out-of-left-field shocks; the film doesn't even bother to telegraph the scenarios, instead just reciting them. Out of desperation, we get Paul Giamatti and a monkey, neither of which are used to much effect. They're just here to pad the running time.
4. Another reason the first film was funny is that it felt legitimately unchained; its most outrageous moments were truly shocking yet believable, the id of boys unleashed in Sin City. As tends to be the case in sequels that don't quite understand why the first films were so beloved, "The Hangover Part II" simply amps up the "outragous" without any real context, turning them more puerile than jaw-dropping. Thus, Ed Helms doesn't just pull out his tooth; now he has a facial tattoo and has sex with a male prostitute. Oooh! Gross! The film doesn't quite get what made its characters fun in the first place either. Bradley Cooper's Phil was a raffish douche in the first film, but he was still loyal to his friends and, through it all, his family; in the end, he was pretty much all talk. Here, with Cooper now a bigger movie star with a reputation to uphold, he's a reaction shot with hair. The biggest disappointment of all is Galifianakis, who walks through most of the movie like he wasn't aware there was a sequel clause in his contract. His presence in the first film was a revelation, a cosmic shot of insanity that kept spinning the movie off in unforeseen directions. Here, Alan is just peevish and weird, lacking any of the radical-angle comic verve Galifianakis specializes in. In the two years since "The Hangover," Alan has turned from an uproarious hallucinatory man-child into Cousin Oliver. It's depressing to watch him.
5. Considering how quickly "The Hangover Part II" was conceived and produced, it was perhaps inevitable that the result would be as slapdash and derivative as it is. There must have been something they could have done with these characters, so enjoyable in the first film, other than simply force them into the exact same situation. (With a monkey.) Maybe you just make it a road movie, let them drive across the country to another wedding or something, meeting all kinds of weirdos along the way. (Shame director Todd Phillips used that for "Due Date.") Maybe they all have to bust Phil out of a Turkish prison, in some sort of comic variation on "Return to Paradise." Maybe you send them to freaking space. Whatever: something. What you don't do is ask the audience to buy that these supposedly intelligent (or at least sentient) characters would find themselves in the same plot as the last film. The first "Hangover" is one of my favorite comedies of this decade, still watchably anarchic any time you turn it on. Its sequel made me sort of hate it, to distrust the creative mindset that allowed both it and this to exist. If you love the first film, seriously, do not see this one. You'll ruin two movies at once.