Two days before his wedding,
bachelor Doug Billings travels to
Las Vegas with his best friends Phil Wenneck, a teacher, Stu Price, a dentist, and Alan Garner, his childish future brother-in-law. Sid, the father of Doug's fiancée, Tracy, lends Doug his vintage
Mercedes-Benz W111 to drive to Vegas. They book a suite at
Caesars Palace and celebrate by sneaking onto the hotel rooftop and drinking
Jägermeister. The next day, Phil, Stu, and Alan awaken, unable to remember the previous night. Doug is nowhere to be found, Stu's tooth is missing, the suite is a mess, a
Bengal tiger is in the bathroom, and a baby is in the closet. They see Doug's mattress impaled on a statue outside, and when they ask for their Mercedes, the valet delivers a
Las Vegas police cruiser. Retracing their steps, the trio travels to a hospital, discovering they were drugged with
Rohypnol, causing their memory loss, and that they went there from a chapel the previous night. At the chapel, they learn that Stu married a
call girl named Jade, despite his relationship with his abusive and unfaithful girlfriend Melissa. Outside the chapel, the trio is ambushed by a gang of men demanding to know where "he" is. Bewildered, they flee and track down Jade, who is revealed to be the baby's mother. The police arrest them for having stolen the cruiser. To get the Mercedes out of impound and an early release, the trio unwittingly volunteer to be targets for a
taser demonstration. While driving the car, the trio discover a naked Chinese man in the trunk named Leslie Chow, who beats them up and flees. Alan confesses that he drugged their drinks to ensure they had a good night, believing the drug to be
ecstasy. Returning to their suite, they encounter
Mike Tyson, who knocks Alan unconscious and demands they return his tiger. After Stu sedates it, they load it into the Mercedes and drive to Tyson's mansion. The tiger awakens, scratches Phil's neck and damages the car. They push the car to the mansion and deliver the tiger. Tyson shows them security camera footage of their drunken behavior from the night before, revealing they lost Doug only after returning to the hotel. While driving back, their car is rammed by a black
Cadillac Escalade manned by Chow and his gang from the chapel. Chow accuses them of kidnapping him and stealing $80,000 in
poker chips. As they deny it, he tells them he has Doug and threatens to kill him if the chips are not returned. Unable to find Chow's chips, Alan, with help from Stu and Jade, uses his knowledge of
card counting to win $82,400 playing
blackjack. They meet Chow in the
Mojave Desert to exchange the chips for Doug, only to find that the "Doug" in question is actually a drug dealer who accidentally sold the wrong drugs to Alan earlier. With the real Doug's wedding set to occur in five hours, Phil calls Tracy to tell her they cannot find him. Simultaneously, Other Doug remarks that someone who takes roofies is more likely to end up on the floor than on the roof, causing Stu to deduce where Doug is. The trio return to Caesars Palace to find a dazed and sunburned Doug on the roof. He was moved there as a joke and forgotten when the roofies wore off; Doug threw his mattress onto a statue to signal for help. Before leaving, Stu arranges to meet Jade for a date the following week. With no flights, the four drive home in the damaged Mercedes, where Doug reveals he has Chow's original $80,000. Despite their late arrival, Doug and Tracy are married. At the reception, Stu gleefully breaks up with Melissa after she sees his tooth gone. Alan finds Stu's camera with photos from their Las Vegas night, and they consent to view the pictures before deleting them. ==Cast==