Holiday comedies are basically a pass/fail situation; almost no movie produced exclusively for people who are already at the mall and feeling seasonally inclined from hearing the Muzak version of "Santa Baby" 18 times is going to be an opus of hilarity. Holiday movies can, however, be really bad (or at least really mediocre, which is arguably worse), so it's not like there's nothing to strive for in the genre. Lucky for Four Christmases, it passes -- not with flying colors, but not by the skin of its teeth either. It's well acted and it's entertaining -- and who can resist a movie where Vince Vaughn and Jon Favreau are brothers, and Robert Duvall is their dad? It probably helps that the premise is fairly unique. Happy couple Brad and Kate (Vaughn and Reese Witherspoon) have a great relationship, full of enjoyed mutual activities like ballroom dance classes and sexual role play. Like a lot of young people, they're long past admitting that their respective families are a zillion kinds of crazy, so every year the two orchestrate an alibi, drop gifts in the mail, and hightail it out of town for Christmas. Unfortunately, this particular year turns out a little differently when their airline gets grounded by fog on the morning of their departure -- an event that would only minorly change their plans, if it weren't for the local news anchor broadcasting live from the airport who catches Brad and Kate in the camera's crosshairs and effectively announces to their families that they'll be very much stuck in town for the holiday. So now, with no excuse to get them out of it, they have to visit all four homes of their collective parents in one day (which is an hour and 22 minutes in audience years). Each household is a different breed of funny/crazy/terrifying, starting with Brad's father, a grumbling old blue-collar retiree played by Robert Duvall. This stop consists of streaking redneck children, dad insisting he can install his own satellite dish, and continued attacks by Brad's amateur UFC brothers (Jon Favreau and Tim McGraw). Next it's off to Kate's mom's house, a WASPish, doily-covered suburban home full of catty passive-aggression and cougary repressed flirtatious outbursts (mostly toward Brad, since all other men in the house have been long since broken). Kate's mom (Mary Steenburgen) has recently discovered religion, which is to say she's dating Pastor Phil, a reverend/local celebrity from the neighborhood Pentecostal rock-concert-style revival church, and this creates an extra dose of weirdness for the couple, when she drags them to mass. So then Brad and Kate visit the next parent on the list, then the next -- you get the idea. It's a cleverly written movie, and outside the awesomely gross vomit gags and just-painful-enough-looking slapstick, there's always the underlying feeling that what you're seeing is eerily familiar. These are people you've been stuck with at parties or meals, trying desperately to avoid talking about politics, money, or any other disastrously substantive topic; the trashy ones who serve food you don't want to touch, the backbiting ones who talk smack about your marital status, the super normal ones who wait years to throw an awkwardness curveball at you by suddenly getting way, way into religion. It's spot-on "funny because it's true" humor, which may not be a particularly genius page out of the comedy playbook, but after a day of unwrapping presents with people who share your DNA -- and sap your will to live -- it doesn't have to be.