Peter (Downey Jr.) is in Atlanta on business, trying to make it back to Los Angeles in time for the birth of his first son. Ethan (Galifianakis) is an oblivious wannabe actor who is looking to find his big break in Hollywood. A series of escalating events gets both of them kicked off their plane, and another series of situations puts them together for a road trip to the City of Angels. Hijinks, and bonding, ensue.
The problem with Due Date is that we've seen this movie before, namely as Planes, Trains & Automobiles. And it was much funnier then. Phillips doesn't really add anything new to the genre, but rather rehashes his Hangover formula onto it in hopes of scoring the same level of laughs (though, it should be noted, I only found The Hangover to be an amusing distraction, nothing more). Phillips also underuses his very talented cast. Downey Jr. has proven that he can be absolutely hilarious (see Tropic Thunder for proof), but here his character is given little to do other than shout and look like he's about to have an aneurysm. Michelle Monaghan, playing Peter's pregnant wife, is mostly ignored (as women tend to be in Phillips' movies), and even Jamie Foxx only has a few short, mildly amusing scenes. It also doesn't help that the movie tries hard to touch the heart, but it feels tacked on and overly sacchrine, and just doesn't fit with the rest of the film. Phillips doesn't commit to it enough to make it feel organic, and the actors too just seem to sleepwalk through those scenes to get to the next joke.
That's not to say that Due Date is a terrible movie. There are some good laughs, and two performers really make their characters work. First off, Galifianakis is great in this role. If you've ever seen any of his stand-up (and I recommend that you do), you'll see that Galifianakis is at his best when he's allowed to improvise his own goofy, non-sequitur one liners (from Live at the Purple Onion: "When you look like me, its hard to get a table for one at Chuck E. Cheese). And that seems to be what he was basically allowed to do here, which provides for some of the film's best lines ("My dad would never do that, he loved me!"). And in a great cameo, Danny McBride mines his Western Union worker for big laughs, even if he's basically playing his Kenny Powers character from Eastbound & Down (or maybe its because of this?).
I couldn't find any pictures of McBride from this film, so you'll have to make due with this.
Due Date is a comedy that will certainly appeal to a lot of people, but its not the funniest or best comedy of the year. And if you're expecting an exact replica of The Hangover, prepare to be disappointed.