Think Oscar and Felix, think Planes, Trains and Automobiles, think Todd Phillips, the director of the runaway hit The Hangover, and you’ve got his latest.Peter (Robert Downey Jr) is a cool architect busy talking via his blackberry to his pregnant wife (Michelle Monaghan) from the back of a limo en route to Atlanta airport.  She’s due in three days and he’s heading home. Ethan Tremblay (Zach Galifianakis) is a clueless slob who’s going to Hollywood, he’s got his father’s ashes in a coffee can, and claims to have “ninety friends on Facebook – twelve of them are pending.” When a series of events cause Peter and Ethan to rent a car together, it’s their strength as two brilliant actors that makes this roadtrip cross-country a worthy theatre ticket.  Murphy’s Law prevails in just about every scene as the cynical Peter slowly evolves into somebody else someplace just outside of Mexico.   Jamie Foxx plays his best friend and Juliette Lewis is perfectly cast as the found-on-Craig’s-list drug dealer.  We’ve seen Galifianakis in this role before.  It’s his niche.  He’s sure of his mission with a certainty and even exhibits facial expressions reminiscent of the late John Belushi.  Like in The Hangover, the movie’s strength is bad guy behavior on a ticking clock. Last time it was a wedding, time it’s a baby.  Three Tiaras