People eat at chain fast-food restaurants because they know exactly what they’re going to get: A cheeseburger from a McDonalds at the Salt Lake City airport tastes exactly like the one from the McDonalds on Ridge Road in Lackawanna and exactly like the one from the McDonalds on Sixth Avenue in Manhattan. That’s what kind of a movie What Happens in Vegas is. You go to see it not because you expect to be surprised by the twists and turns of the plot, or to see the cast playing against type, but because you know exactly what it is going to be. You may also avoid it for exactly the same reason, and you would be equally justified in doing so. Ashton Kutcher and Cameron Diaz star as New Yorkers suffering differing degrees of stress. She’s a Wall Street control freak who has just been dumped by her boyfriend. He’s a slacker who gives up on everything at the first whiff of failure. A drunken encounter in Las Vegas leads to a marriage that they are forced to stay in for six months due to a plot mechanism I won’t give away simply because it’s the only thing about the movie you might not be expecting. Familiarity may breed contempt in real life, but never in movies like this, and after a few reels of grating on each others nerves the friction leads to sparks. Diaz and Kutcher bring to their performances exactly what their fans will expect, though the former is approaching her shelf limit for this kind of cutie pie role. The director is Tom Vaughan, who has mostly worked in television, appropriate to the project at hand. The script is by Dana Fox, whose previous credit was The Wedding Date, which indicates either that she’s hit on a formula or that she has issues she needs to work on with her therapist.

—m. faust