Alonso Duralde Film critic

It’s no revelation that Hollywood movies are so often boring because Hollywood stars have such a burning need to be likable. “What Happens in Vegas,” for instance, starts out as a promisingly caustic battle-of-the-sexes comedy — “The War of the Roses” for the Teen People generation — but ultimately turns into a big puddle of mush because the characters played by Cameron Diaz and Ashton Kutcher have to become all nicey-nice in the final act.

Diaz stars as Joy, the kind of type-A anal-retentive New Yorker who schedules time to make schedules. She endures an excruciating breakup with her boyfriend (Jason Sudeikis), who dumps her at their doorway while all of their friends are hiding inside at his surprise birthday party. Meanwhile, Brooklynite Jack (Kutcher) has just been fired from his furniture-building job by the owner of the company. Who happens to be Jack’s father (Treat Williams).

For script-convenient reasons, these total opposites wind up hanging out together in Las Vegas, where they hope to blow off the steam of recent disappointments. In vulnerable states, they open up to each other about their problems. They drink a whole lot. And then they wake up married to each other. But just as they’re about to part ways and Google “annulment,” Joy gives Jack a quarter, which he puts in a slot machine that hits a $3 million jackpot.

Quick facts Starring: Cameron Diaz, Ashton Kutcher, Rob Corddry, Lake Bell, Dennis Farina Director: Tom Vaughan Run time: 1 hour, 39 minutes MPAA rating: PG-13

Back in New York, they bicker over who gets the money, and an unamused judge (Dennis Miller) orders them to live together for six months and to have regular visits with a marriage counselor (Queen Latifah, barely hiding her ennui). Only if Joy and Jack show that they aren’t taking their vows lightly — “Gay people aren’t destroying the sanctity of marriage,” notes the jurist, “you people are” — will he make a judgment.

Joy and Jack’s attempts to make the other quit the marriage and abandon claim to the money makes for the best bits of “What Happens in Vegas,” even though the cash seems like it would be small potatoes to Joy, who’s on the fast track to promotion at her commodities-trading company. But whatever acidity can be mustered by Dana Fox’s script and Tom Vaughan’s direction gets completely nullified by Joy and Jack eventually falling in love and teaching each other valuable life lessons. Yawn.

Video   Diaz, Kutcher revisit ‘Vegas’ May 5: Cameron Diaz and Ashton Kutcher explore themes behind their new movie, "What Happens in Vegas." Today show

While Diaz and Kutcher work through their stock repertoire of winsomeness, the second bananas steal the show. From Lake Bell and Rob Corddry as their respective best pals to Miller, Sudeikis and Zach Galifianakis (the latter as a pal of Jack’s who’s hopelessly smitten with Joy), it’s the wonderful supporting cast that makes “What Happens in Vegas” even remotely worth seeing.

What would mainstream rom-coms do without actors like these (and Parker Posey and Judy Greer and Romany Malco and Zooey Deschanel and Wanda Sykes and Steve Zahn) who are willing to risk likeability in favor of being fast and loose and sassy and funny? They’re the free cocktails that keep us rolling the dice after the above-the-title names have already crapped out.

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