A Guy Thing (2003)

Paul Morse is a good guy. When his friends throw him a wild bachelor party, he just wants to keep his conscience clean -- which is why he's shocked when he wakes up in bed with a beautiful girl named Becky and can't remember the night before. Desperate to keep his fiancée, Karen, from finding out what may or may not be the truth, he tells her a teensy lie. Soon his lies are spiraling out of control and his life is a series of comical misunderstandings.