Todd Phillips's films have generally represented missed opportunities for examination of masculine angst, setting up conflicts which, while initially relatable, are eventually abandoned in favor of intensive male-bonding sessions. Their progression has been predictable, from high-school-sweetheart separation anxiety (Road Trip) to college-separation anxiety (Old School) to the marriage terror of The Hangover, but this gradual slide into adulthood hasn't necessarily been accompanied by any growth. Each new movie finds a fresh set of guys, fearful of change and responsibility, learning muddily defined lessons about what it means to be man.
Due Date employs the same setup, with father-to-be Peter Highman (Robert Downey Jr.) launched into a trial run at parenthood after he's forced to drag man-child Ethan Tremblay (Zach Galifanakis) across the country, where Peter's wife is preparing to give birth to their first child. First crossing his path at an Atlanta airport, the bumbling Ethan gets Peter in trouble at security, shot by an air marshal and eventually placed on the dreaded no-fly list.
Tied together by necessity and some dim shreds of humanity at the bottom of Peter's dark, wryly brutal soul, the two find themselves linked, splitting a rental car and swapping driving duties. This allows the film to indulge in a routinely vicious first hour, the dissonant clashing of idiot versus asshole ringing out over one crudely sketched set piece after another. Ethan is, of course, an imbecile, a clueless aspiring actor with a baffling perm, who insistently believes that the Grand Canyon is manmade. Peter, however, is just as bad, a sneering jerk who argues with veterans, hits children, and spits on dogs.
These roles play out as grossly exaggerated versions of the actors' comedic personalities (or in Galifanakis's case, a brasher reprisal of his role from The Hangover), beyond which a kind of troubling transference seems to be at work. Ethan, with his little dog and feminine walk, stands in for all that is strange and frustrating, a naïve weirdo constructed to absorb scorn. Up against this kind of obstacle, the harried Peter becomes, in the Adam Sandler The Water Boy mold, an irate audience avatar, his bad behavior justified because it's directed toward such an irritating figure.
The implication seems to be that Peter, saddled with the requisite issues from his own father, needs the unbearable Ethan as practice, a misbehaving child he can beat and abuse to cleanse himself for the coming of his own. Yet unlike the rollicking indulgence of The Hangover, Due Date actually has some lessons in mind, and to its credit handles the requisite third-act dramatics far better than most comedies. Peter's passage from arrogant cruelty to tempered grouchiness is staggered across the film's second half, where he stutter-steps from violence to compassion.
Most surprisingly, Phillips manages to wrench moments of real pathos from Tremblay, whose big dreams and recently deceased father (whose ashes he carries around in a coffee can) eventually make him human. It's a little crude to see the character's weirdness being exploited for drama after so readily being jabbed for cheap laughs in the first half, but by the end, Due Date has settled into a rough if credible buddy film, one that if not necessarily very funny at least washes off the stink of its initial nastiness.