Robert Downey Jr. has signed up for the Todd Phillips comedy Due Date, which already stars Zack Galifianakis. Yes, the hottest comedy star of last summer (in Tropic Thunder) is joining the hottest comedy star of this summer (in The Hangover) for what we’re guessing could be a pretty hot comedy as early as next summer.

Due to shoot this September in Atlanta, Arizona and LA, the film sees Downey Jr. cast as a father-to-be who’s racing to get home for the birth of his child, along with Galifianakis’ mismatched travelling companion. Phillips describes it as a “buddy comedy without the buddies”, so think Planes, Trains and Automobiles with birth instead of Thanksgiving at the end of it.

The script was written by Alan R. Cohen and Alan Freedland, and revised by Scrabble-winning scribe Adam Sztykiel.