Due Date, starring Robert Downey Jr. (Iron Man 2) and Zach Galifianakis (The Hangover), is essentially a modern retelling of the 1987 John Hughes classic, Planes, Trains and Automobiles. In that hilarious odd couple comedy, Steve Martin was a road weary salesman struggling to get home for Thanksgiving and, at the same time, trying to rid himself of a well-meaning but lecherous misfit, played by John Candy. The movie is memorable for the “where are your hands” motel scene, as well as Steve Martin’s f-word diatribe in the rent-a-car line. And while that movie had some mean moments, Due Date’s retelling, albeit most likely unintentional, shows viewers that if art imitates life, 23 years later we’re meaner, more puerile and grouchier than ever before.

The meanness I speak of emanates enthusiastically from Peter Highman (Robert Downey Jr.), a Bluetooth-wearing, modern-day busybody. We never really know what Peter does for a living, but it’s not important – he’s curt, distracted, rude and insecure, an archetype of today’s middle-aged Banana Republic brigade. Peter is on his way home to Los Angeles to be with his wife (Michelle Monaghan), as she is due to give birth to the couple’s first child. On the flip side, we’re introduced to Ethan Tremblay (Zach Galifiankis), a happy-go-lucky man-child who is as airheaded as he is a magnet for random destruction. The difference, as we come to discover through the movie, is that Peter chooses to be a jackass, while Ethan is who he is and offers no apologies. Yes, he’s annoying and yes anyone who openly masturbates in the passenger side of a rental car should automatically be blacklisted, but a kind, caring heart covers a multitude of sins, whereas Peter’s self-serving thinking and insults simply highlight his repugnant heart.

Peter and Ethan’s adventure begins when the duo is kicked off an airplane by a sky marshal and put on the TSC’s (Terrorist Screen Center) controversial “no fly list.” To make matters worse, Peter’s wallet is stuck with his luggage on the flight he was booted from, so he has no ID, no money and not a lot of options. He decides to hitch a ride with the talkative, quirky Ethan who, aside from taking his dad’s ashes to the Grand Canyon, is also heading to Hollywood to become an actor. As the pair crisscross the Gulf States into Texas and on to California, they meet with every conceivable problem and destruction, most of which is caused by Ethan’s penchant for marijuana, thoughtlessness and falling asleep at the wheel. These moments aren’t so much funny in a jovial, ha-ha sort of way, as they are in a voyeuristic, YouTube generation, open-mouthed, I-can’t-believe-they-showed-that sort of way. Most of the time we’re not laughing at Ethan but rather at Peter, who, in devilish retribution, says and does things we all dream we could do, but, thankfully, have the common decency to restrain ourselves from.

Downey Jr. proves again he is capable of acting in any capacity and any genre. Watching him portray Peter, you realize he puts his whole energy and effort into the character and doesn’t just show up to collect a paycheck. He is easily one of the finest actors working today. As for Galifianakis, who seems to always play the same Alan Garner-esque character, he actually brings a rawness and vulnerability to Ethan that isn’t akin to the reckless dimwit he portrayed in The Hangover. In fact, one of the movie’s more touching scenes, wherein Ethan breaks down over the death of his father in a rest stop bathroom, had me wondering if Galifianakis was truly having a tearful moment. It was truly heartbreaking.

Many moviegoers might be tempted to see Due Date because of the glory, laud an honor director Todd Phillips received with his last feature, the ever-popular dudes-gone-wild comedy, The Hangover. Trust me when I say The Hangover, and all of its hilarious obscenity and ever-present destruction, feels like a burst of sunshine compared Downey Jr. and Galifianakis’ road trip from hell. Due Date is very much a dark comedy and while it has moments of hilarity and heart, it feels disjointed and hurried, like a half-hearted bookmark between The Hangover and The Hangover 2.