Remember Return to Oz, the sequel to The Wizard of Oz? The Hangover: Part II is a lot like that. It didn't need to be made, it makes the characters from the first film look like quantifiable douche-pagodas, and, inexplicably, it's brimming with Wheelers.

Everyone remembers the first Hangover film, partly because Zack Galafanakis is a drug and to mainline a snifter of his sweet tang is to lap unashamedly at a pond of pure, comedic, beardy brilliance. But mostly, people remember The Hangover because, much like a Trojan Horse, it took us by surprise. And, like a Trojan Horse, it was left in the courtyard of our expectations, wherein it waited until nightfall before the Trojans of comedy spewed out, generally wreaking havoc. In a manner of speaking.

You see, The Hangover followed Phil (Bradley Cooper), Stu (Ed Helms) and Alan (Zack Galifanakis), as they woke up in Las Vegas with no recollection of a biblically nasty bachelor party, during which they lost the bachelor, pissed off several criminals, stole a tiger from Mike Tyson and did a couple of hundred other things which were illegal and/or violent. The film managed to pitch up a moronic (well, at the very least, a terminally base) premise - i.e., three guys being buffeted around Las Vegas amongst a sea of strippers and errant dental mishaps - and carry it off with a boatload of heart. Phil, Stu and Alan were three incredibly disparate characters who, by rights, shouldn't have worked together as a group. Phil: jock. Stu: nerd. Alan: autistic mental patient in sensible shoes.

And the joy people felt after seeing the first film was, frankly, because these stock characters were loaded up with such realism, and performed so superbly, that you found yourself loving them (or, at the very least, liking them more than you initially wanted to). And they evolved! Much like a Bulbasaur evolving into an Ivysaur, the characters grew from their experiences; Stu, in particular, stood up to his relentless harpy of a wife, which segues quite nicely into where The Hangover: Part II begins: with the impending wedding to a loving woman for Stu. He's engaged to Lauren (Jamie Chung), whose parents have insisted on a wedding in Thailand, on an idyllic beach, on an idyllic island.

And this is where it goes wrong, on two levels. The first is part of the plot; the boys wake up in a seedy hotel room in the middle of Bangkok, with no memory of what went down the previous night. But also, by this point in the story, it becomes evident that the camaraderie the first film so richly earned is being totally squandered. It's as if the emotional odometer on each character was wound back to zero before the story started, meaning all the journeying and development they went through has been dispensed with. Phil has been de-evolved into a meaner, flatter and swearier version of himself. Alan is fine, although his mental retardation does appear to have gotten worse, but this seems to be because Phil and Stu, apparently best friends at the close of the first film, haven't talked with Alan in years. And from a plot perspective, Stu has every reason to be a new man. But his behaviour has, as seen in Phil, been dialled right back to zero; he's as unassertive as he was in the opening scene of the first movie.

Defenders of the film will say that this is to allow newcomers to see clear, clean character types. After all, not everyone has seen the first film, and you need to give them an 'in'. These defenders are idiots, however, given that the film is called THE HANGOVER: PART II. It's not even labelled as a separate entity, it's pitching itself as a direct continuation of the first story. And if that's the case, why is the film so mind-shatteringly grim? Instead of a comedic jaunt peppered with bizarre, occasionally brutal and always wonderfully stupid recollections and predicaments, it's like Todd Phillips (the director) has been inhabited by Guy Ritchie. The film is shot like a jaunt through a grimy, sooty fugue, and when the boys wake up after their night in Bangkok, they're battered with some of the most traumatic, unfunny bullshit I've seen in quite a while. It's like watching a drunk friend periodically pass out whilst talking to you; occasionally they'll be cogent, and you'll see the sense of what they're saying. You'll even recognise the person before you. Maybe you'll even laugh at them. But then, mid-sentence, they'll black out again, and you'll see their dead eyes lolling about insanely. And you'll just sigh and try to enjoy your sandwich.

The real problem is the script, which labours under the misapprehension that in order to be funny, and in order to function as a whip-smart sequel to a comedy about depravity, you need to (a) be more depraved, and (b) you need to be 'gritty'. But with The Hangover: Part II, the depravity is handled humourlessly (there are exceptions, obviously, but they're too few to mention), and the film is genuinely so gritty that for about twenty minutes, I thought I was watching a really decent crime thriller about amnesia and loss in the heart of an unforgiving Bangkok. It's at times nightmarish, and not in an ironic way.

However, all the actors in the film are wonderfully talented. The trio of leading men all hit their marks, which is tough to watch, when you can tell that Ed Helms in particular is given some monumentally average dialogue to deliver. Even the supporting characters (most notably Ken Jeong, of Community fame) have loads of appeal, but the script sags like a wet cardboard box. The first film wasn't a work of art, but it was surprisingly funny, and you were left with a sense of completion; it was a buddy movie. Whereas The Hangover: Part II feels more like a Bangkok tourism project pitched at rapey frat boys. This film needed to be made about as much as I needed to dedicate almost a thousand words articulating its simmering mediocrity.

- One and a half stars


The Hangover: Part II opens in cinemas Thursday, May 26.