Downey Jr., Galifiankis try to meet 'Due Date'

Robert Downey Jr. is trading in famous fictional characters for a road trip.

The actor, who will star as "Sherlock Holmes" and Tony Stark in "Iron Man 2," will team up with "The Hangover" star Zach Galifianakis for "Due Date," according to Variety.

See pictures of Robert Downey Jr. in 'Sherlock Holmes.'

The pair will play mismatched buddies racing to get to the birth of Downey's character's child. Hey, Robert: Whatever you do, don't drink any Jagermeister Zach offers you.

Expect the movie to be a raunchy comedy: "Due Date" will be directed by "Hangover" helmer Todd Phillips.

Production begins later this year.

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