Review: 'Due Date' road trip feels endless

Robert Downey Jr. is miserable, stuck on a cross-country drive with a creepy Zach Galifianakis in the comedy "Due Date." And it's easy to imagine how he feels: It's often torturous just sitting through the movie, and we're not the ones trapped in the middle of Texas with the guy.

From the commercials alone, though, it's clear we're probably going to be in trouble here: They cut away early and often to a French bulldog in all his smushy-faced, bat-eared adorableness. When you need to go to the dog for easy, reliable laughs, there's something wrong with your script — and this is coming from a dog person.

That script comes from director Todd Phillips, hot off the success of "The Hangover," and three other writers. But "Due Date" lacks the consistent hilarity and originality of that last-summer hit; it's got some individual laughs here and there but lacks sufficient story or character development to hold the whole endeavor together.

And it's not as if "Due Date" were all that complicated — it shouldn't have been so difficult to get right. It's a simple mismatched-buddy road trip movie, the kind you've seen countless times before. Downey plays Peter Highman, a stylish, uptight architect whose wife (Michelle Monaghan) is about to give birth to their first child. Galifianakis plays Ethan Tremblay, a clueless aspiring actor Peter bumps into, literally, at the airport in Atlanta.

Through a series of massive contrivances — the kind that plague the entire journey — Peter and Ethan are kicked off the plane, placed on the no-fly list and forced to share a rental car all the way back to Los Angeles. This includes a stop for Ethan to pick up some medical marijuana for his "glaucoma," a major car accident, an awkward afternoon with Peter's wife's ex-boyfriend and an unplanned and unwise excursion across the Mexican border at night.

These side trips can be amusing for the casting choices alone, which are often inspired. But they also make you wonder, how could that possibly happen? And: Why would anyone do that? And: Will Ethan ever resemble a real person who exists on this planet? He's more like a cluster of idiosyncrasies — he orders waffles at the Waffle House, even though he's allergic to waffles, for example. He masturbates to fall asleep even though Peter is sitting in the front seat of the car right beside him (cue the cutaway to Ethan's dog doing the same thing). He's simultaneously high-maintenance and socially inappropriate. The comparison has been made between "Due Date" and "Planes, Trains & Automobiles," but it's actually got more "Rain Man" in it: Peter has his perfect life upended by a demanding, overgrown child with a heart of gold (or so we're meant to believe — Ethan's more annoying than anything else).

Galifianakis has made a career out of playing variations on this character: a weird guy who says and does all the wrong things but probably means well deep down. Usually, the shtick works, as it did in "The Hangover" and in Galifianakis' own online talk show "Between Two Ferns." But there's a fine line between making people feel intentionally uncomfortable for the sake of comedy and being just plain unpleasant, and he crosses it this time. You would not want to drive down the street with this guy, much less across the country, which makes "Due Date" feel interminable.

Downey does as much as he can with his underwritten, straight-man role — even as "Due Date" veers from slapstick to feel-good — simply because he's such a smart, clever actor. Even though he's called upon to do some unlikable and even cruel things, he's fascinating to watch through his sheer magnetism, and through a screen presence that always offers the promise of the unexpected.

"Due Date" also goes some places you wouldn't expect. But you might not want to go along for the ride.

"Due Date," a Warner Bros. Pictures release, is rated R for language, drug use and sexual content. Running time: 95 minutes. Two stars out of four.