This probably depends on your sense of humour and it's certainly not mine. It's the same plot as "Planes, Trains and Automobiles", where a conventional man is forced to travel with a slob. That was funny. The main reason why Due Date fails is because the Ethan Tremblay (Zach Galifianakis) character is not at all endearing, only stupid and crass in an entirely non-funny way, and Peter the "conventional" half (Robert Downey Jnr) is equally unlikeable. In fact it's embarrassing and cringe-worthy. What's funny about taking drugs, thumping a child in the stomach, or doing things in public that are usually kept in the bedroom? I can't agree with the reviewer who said "if you like The Hangover you'll like this" because I laughed a lot in The Hangover, but only once in Due Date: when Peter says to Ethan "The Mississippi isn't in Texas, it's in Mississippi." That's how desperate I was to laugh. It's ludicrous to think Ethan would have been given a job as an actor, and the clip they show of him in a prime-time show is as unfunny as the rest of the film.