The previews would have you believe that you're in for a nasty comedy on the order of The War of the Roses, but who is the studio kidding? It's another predictable romantic comedy, one that insists that spending time locked into an unhappy marriage doesn't breed contempt, but sows love.
Cameron Diaz plays Joy McNally, whose engagement to upscale Mason (Jason Sudeikis) fizzles. Meanwhile, serial booty-caller Jack Fuller (Kutcher) is feeling down following the latest lecture from his father (Treat Williams). Joy and Jack each get a pep talk from their friends (played by Lake Bell and Rob Corddry, respectively) resulting in a vacation getaway to the place where anything goes. As Jack correctly notes, "What happens in Vegas you pay for when you get home. That's what the thing is."
Indeed, Jack and Joy meet (under bad circumstances), go out on the town, drunkenly marry, then jointly hit a slot-machine jackpot. Back home in New York, the pair would like a quickie annulment, but an ornery judge (Dennis Miller) freezes their $3 million winnings until the couple has spent six months as man and wife. Wackiness ensues, as the odd couple make each other miserable. Despite such tender sweet nothings as "Hey, don't get hit by a bus. Or do. Whatever," the couple inevitably falls in love. Maybe this development has something to do with their common feelings of inadequacy, but that's a question the film seems afraid to explore in any depth.
What Happens in Vegas is a big comedown for Tom Vaughan, the director of the charming Starter for 10. Like so many modern comedies, this one hopes to buy its way to funny by hiring proven quantities like Corddry and Zach Galiafanakis to be trained monkeys. As funny as they are, and as committed as the leads are, there's no substitute for a smart and shapely script, which Vaughan sorely lacks here. When Vegas tries to be sincere, it only reveals the disconnection from reality of its commercial enterprise. Try not to retch when one of the characters admits to the other, "You bet on me…and you made me want to bet on myself."