It tells the story of Phil Wenneck (Cooper), Stu Price (Helms), Alan Garner (Galifianakis), and Doug Billings (Bartha), who travel to Las Vegas for a bachelor party to celebrate Doug's impending marriage. The film stars Bradley Cooper, Ed Helms, Zach Galifianakis, Heather Graham, Justin Bartha, Ken Jeong, and Jeffrey Tambor.
It is the first installment in The Hangover trilogy. The Hangover is a 2009 American comedy film directed by Todd Phillips and written by Jon Lucas and Scott Moore.