The Synopsis :
Doug (Justin Bartha) is about to be married, so his friends -- Stu (Ed Helms), a dentist planning on proposing to his girlfriend of three years, Phil (Bradley Cooper), a schoolteacher bored of the married life, and Doug's soon to be brother-in-law Alan (Zach Galifianakis), who is smart yet socially-inept -- take him to Las Vegas for a bachelor party. Stu's girlfriend is very controlling, thereby forcing Stu to lie to her about their destination.The guys get a suite at their hotel, then sneak on to the roof of the hotel and toast to the night ahead. Skipping forward to the next morning, the three groomsmen awake with no memory of the previous night. They find Doug missing, Stu missing a tooth, a tiger in the bathroom, and a baby in the closet. Initially they believe Doug to have gone out for breakfast, but soon worry when his cellphone has been left behind. They collect what memories they have to figure what happened to Doug. The valet brings them a police car, which they had dropped off the night before.Because Phil is wearing a hospital bracelet, the guys head to the hospital. The doctor identifies roofies in their blood, and tells them that they had just come from a wedding. At the chapel, they learn that Stu had married a girl named Jade (Heather Graham). On the way to her place they're attacked by two Chinese thugs. They escape and find her, where she reveals she's a hooker and the baby is her's. Cops bust into her apartment to arrest the three men for stealing their car. However, not wanting to face the embarassment of losing their car, they work out a deal in which the men volunteer to demonstrate how tasers are used. Afterwards they pick up their car in good shape, though a Chinese man named Mr. Chow (Ken Jeong), is locked in the trunk and attacks them upon his release. Alan admits to having drugged their drinks the night before, hoping they'd have a better time, but had been sold Roofies by accident.
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