In New York City, high-strung commodity futures trader Joy Ellis McNally is dumped by fiancé Mason at the surprise birthday party that she threw for him.

Both Joy and Jack are distraught and take debauched trips to Las Vegas with respective best friends Toni "Tipper", who is a bartender, and Jeff "Hater", a lawyer.

Once the misunderstanding is cleared up and receiving upgraded rooms and coupons to various clubs, they party and drink together and end up getting married.

Before they divorce, Jack uses a quarter Joy gives him in a slot machine, hitting a three million dollar jackpot.

The judge declares they cannot divorce until they attempt to co-exist for six months, while attending weekly sessions with marriage counselor Dr. Twitchell.

The judge decides they will split the remaining 1.4 million dollars (after taxes, bills Joy ran up, and money Jack spent on his new woodworking business).

American Big Brother 9 housemates Ryan and Sharon were given a special screening of the film after winning a "luxury competition" in April.

[6] In its opening weekend, the film grossed $20.2 million in 3,215 theaters in the United States and Canada, finishing second at the box office behind Iron Man.

The site's critical consensus reads, "What Happens in Vegas has a few laughs, but mostly settles for derivative romantic comedy conventions and receives little help from a pair of unlikable leads.

[9] Manohla Dargis of The New York Times slammed it, stating that What Happens in Vegas is "one of those junky time-wasters that routinely pop up in movie theaters".