Justin Bartha is in The hangover Part III.
Justin Lee Bartha ( born July 21 , 1978 ) is an American actor , known for his roles as Riley Poole in the National Treasure film series , Doug Billings in The Hangover trilogy , and David Sawyer in the NBC comedy series The New Normal . The Hangover Part III . The film stars Bradley Cooper , Ed Helms , Zach Galifianakis , Justin Bartha , and Ken Jeong .