Recipe for nutso fun: Mix Zach Galifianakis with Robert Downey Jr. Apply the same mold John Hughes used for Planes, Trains and Automobiles. Have Todd Phillips stir with wack-ass abandon. Don't worry about missing ingredients, like plot. Serve to an audience ready to lap it up.

There you have Due Date, a raucous ride built out of used parts and bizarre shifts in tone but driven by two comic virtuosos who know that the best laugh riffs rise from a baseline of character. Director and co-writer Phillips (Road Trip, Old School) realizes his new movie has an 800-pound monkey on its back. That would be The Hangover, the 2009 farce that came out of nowhere to sprinkle Galifianakis with stardust and rule the world. Is Due Date the new Hangover? It is not. But it has its own rewards.

They all have to do with the interaction of the lead actors. Downey plays Peter Highman, a stressed-out suit in a hurry to leave Atlanta and get home to Los Angeles, where his wife (Michelle Monaghan) is about to give birth. Is he the father, or is it his BFF (Jamie Foxx)? Don't care. You won't either. What matters is that Peter meets Ethan Tremblay (Galifianakis), a wanna-be actor and full-fledged pain in the ass who gets them kicked off a jet and sharing a car to L.A. When they aren't out to kill each other, they grudgingly reveal their secret hearts. Sugar shock? Sometimes. But when Peter pushes Ethan into improvs to prove he can act, or the two just let their emotions bleed, Galifianakis and Downey gift Due Date with something rare in any kind of movie: a soul.

“(We're Not) The Jet Set”

George Jones and Tammy Wynette were still married when they recorded the tongue-in-cheek "(We're Not) The Jet Set." The lyrics, written by Nashville songwriter Bobby Braddock, who also penned Wynette's "D-I-V-O-R-C-E" and Jones' "He Stopped Loving Her Today," make fun of the good life by declaring, "We're not the Jet Set/We're the old Chevrolet set." Braddock recalled that while writing the song, he needed the name of a city that evened out the rhyme he had with "Riviera" and "Missourah." “I got out a Rand McNally atlas," he said. "In the first part are the maps. The last part is an alphabetical listing of cities. I wanted a rustic, small-time sound. I went to the listing for Missouri. And I found 'Festus.' I loved the sound of it."