Some movies could be very good, except for a single flaw that dooms the whole production to failure. Four Christmases isn't one of them, but it's a very close cousin: though it could never, in its current state, be a very good film, there's an obviously good film lying just under the surface, always threatening to erupt but only coming out in brief flashes.

This first became obvious to me in the scene where we meet our protagonists: Brad (Vince Vaughn) and Kate (Reese Witherspoon), a very loving unmarried couple, are taking dancing lessons, and radiating their obvious affection for each other to a degree that the other two couples in the dance studio can't help but ask when the wedding date is. They are taking lessons for their wedding, of course, and they are acting like a sappy pair of newly-engaged lovebirds, right? Wrong, say Brad and Kate: marriage sounds like a love-destroying prison and the very notion of having kids is entirely contrary to everything either of them have ever wanted. This is exactly what the other couples do not wish to hear, and it's obvious from their faces that these sentiments are seriously undercutting their commitment to this "matrimony" idea. Brad and Kate, lost in their happy reverie, hardly seem to notice.

For something like two-thirds of this scene, I thought I was watching a film about a pair of genial misanthropes, enraptured loves with a great joy for mocking lesser beings, and I was absolutely delighted. It promised to be an adventure in dark sarcasm, with two mean-spirited anti-heroes headlining a holiday-flavored black comedy - and given that the film's entire premise is based on the idea that Brad and Kate effortlessly and without moral compunction tell the most outrageous lies to their families (and, we learn, to each other), it's not hard to shake the feeling that we're supposed to find our leads to be outrageously, charmingly bad. But then, the rest of the scene makes it extremely obvious that they have no idea that they've upset the others so badly, and my initial hopes were dashed in favor of a similar but entirely different movie about basically good people who sometimes make mistakes, but don't really have harm in their hearts.

I obviously don't know this for a fact, but I have my suspicions that the original story of Four Christmases, by first-timers Matt R. Allen & Caleb Wilson, was very much a coal-black comedy about a pair of appealing assholes, and probably at least the first draft or two. But then some studio executive got to worrying that nobody would like a Christmas movie about a pair of humorously awful people, and by the time the shooting script was finished (with Allen & Wilson sharing a credit with Jon Lucas and Scott Moore), it had been horribly mutated into a tremendously run-of-the-mill family-friendly comedy (ah, but with a naughty PG-13 twist!) with the dreary twin themes that a) nobody who lives in the city can be emotionally fulfilled, and b) if you're any kind of remotely worthwhile human being, you will GET MARRIED and HAVE CHILDREN, else you're nothing but some kind of horrid yuppie Communist.

But structurally, the film still has this old idea of gleeful misanthropy undergirding it, and it's in the moments when Four Christmases (incidentally, I know that's the proper spelling, but something about that "-mases" keeps bugging the hell out of me) is furthest from the warm fuzzies and closest to the nasty-minded sarcasm that it rises above the standard-issue holiday pablum to gesture in the direction of something much funnier and more entertaining. Again, these are nothing but my suspicions; but still, Vince Vaughn's presence doesn't count for nothing, and he does "misanthropic sarcasm" a hell of a lot better than he does "cute and warm family stories", and everybody knows this, and why else would he have been cast?

For indeed, it's the casting more than it's paint-by-numbers screenplay that truly dooms Four Christmases. Vaughn and Witherspoon are plainly uncomfortable in their roles, they obviously don't like each other very much, and this results in two of the flattest performances of any romantic comedy of recent vintage, hampered by perfectly neutral chemistry - they don't spark with each other, but they aren't so mismatched as to present the bad-movie spectacle of anti-chemistry, either. The film hedges its bets a bit by casting some grand movie vets as their parents - oh, I forgot to mention the plot. Brad and Kate are going to Fiji, but their flight is canceled and all their lies to their families unravel, and they have to spend Christmas with all four of their divorced parents, hence the title - including Robert Duvall, Mary Steenburgen, Sissy Spacek and Jon Voight. Of these, Spacek is perhaps the most delightful to watch (Duvall is given the worst-written role, Voight the smallest), but none of them are onscreen all that long, while Vaughn and Witherspoon are constants, and the film rather quickly descends into an 82-minute game of "Who's Got The Next Cameo?"

By and large, the film is too mediocre to be genuinely bad, and there are just enough half-way decent lines and reaction shots to keep it squarely in the "not entirely grueling" camp. But by and large it's a flaccid mess, pushed forward by director Seth Gordon - making his feature fiction debut after some shorts and the magnificent documentary The King of Kong - with relentless energy that privileges story momentum over all such trivial concerns as character or comedy. It's like the movie wants to get over as quickly as possible, and frankly, I don't blame it. It comes so close to having any kind of spark at all, but in the end this is nothing but a bland, typical Christmas movie: lazily conservative, privileging saccharine platitudes over a beating heart.