In Due Date, a highly strung father-to-be Peter (Robert Downey Jr) is forced to hitch a ride with an oddball aspiring actor Ethan (Zack Galifianakis) on a disastrous cross country road trip, in order to make it to the birth of his child on time.

The astounding global success of The Hangover has burdened director Todd Phillips with a huge weight of expectation. People simply expect to be laughing long, hard and often at his films. Due Date offers some good quality laughs, but not as frequently as some may have hoped. It’s a little darker and more sullen in tone than the zany silliness of The Hangover.

Much of the success of The Hangover has been attributed to the bearded insanity of funnyman Zack Galifianakis and Due Date also relies heavily upon his nuanced awkwardness for laughs. The key to good ‘buddy movies’ is that not only do we have to feel sorry for the normal guy stuck with some irritating loser, we also have to feel sorry for the loser. It’s a fine art to be obnoxious and sympathetic at the same time but Zack Galifianakis manages it fairly well. He has the sort of pathetic vulnerability that makes it impossible to loath his moronic oafishness.

In sharp contrast, Robert Downey Jr has emerged from the shadow of a bad boy reputation to establish himself as one of Hollywood’s most charismatic and effortlessly cool leading men. Sublime star turns in Iron Man, Tropic Thunder and Sherlock Holmes have helped him become the household name he has always deserved to be.

It’s an oversimplification to say that Peter (Downey Jr) simply plays the straight man to Galifianakis acting weird. There’s a furious and slightly unhinged quality to Peter. He’s essentially a good guy, but he’s not above punching a child or rage induced animal cruelty. A less likeable actor could have easily left the character feeling like a hysterical bully.

Due Date’s plot and characters draws obvious comparisons with classic road movie “Planes, Trains and Automobiles”, but its grungy gross-out humour doesn’t have quite the same warmth to it. It’s certainly interesting watching our mismatched duo lurch their way through a series of escalating fiascos but it’s not always joyous.

If you’re a fan of The Hangover, Due Date might just offer you more than the disappointing repetition of The Hangover Part 2. If you don’t quite get the Hangover hype then you really won’t get this either.