“What Happens in Vegas”

Whether that represents a win or a loss depends on your perspective. (I know which side I’m on.)

If you’re just looking for upbeat fluff featuring two decorative stars — and you thought “Fool’s Gold” was a cinematic blast — then “What Happens in Vegas” should be just your fruity frozen drink from the casino bar. (In the tacky take-home souvenir glass, of course.)

But if you’re looking for a blithe romantic comedy with some smarts to go with the screwball antics, then abandon hope all ye who enter here.

Although most of “What Happens in Vegas” really happens in New York, the premise wouldn’t work without the Neon Nirvana setting. After all, what other city provides a more logical place to get plastered and marry someone you hardly recognize?

That’s exactly what happens to our designated sweeties, Jack and Joy (hey, at least they didn’t name her Jill), played by Ashton Kutcher and Cameron Diaz.

He’s a slacker who’s just been booted from the family business — by his own father (Treat Williams). She’s a hard-charging commodities trader who’s just been dumped by her snooty fiancé (“Saturday Night Live’s” Jason Sudeikis) — at the surprise birthday party she organized for him.

So where do bummed-out (him) and brokenhearted (her) New Yorkers go when they need to blow off steam? Vegas, baby, Vegas!

Naturally, Joy and Jack don’t go alone. She’s accompanied by her wisecracking pal Tipper (the appealingly deadpan Lake Bell). He’s accompanied by his wisecracking pal Hader, aptly nicknamed Hater (Rob Corddry, in a role he could play on autopilot). And once they hook up in Vegas, this fearsome foursome hits this crazy town in decidedly crazy fashion, as they limo from nightclub to pool to nightclub — to wedding chapel.

As the Oscar-winning theme song from “The Poseidon Adventure” reminds us, however, there’s got to be a morning after — and when it finally shows up for the just-married Jack and Joy, they awaken to the horror of what they’ve done. And, what they must do: get an immediate annulment.

At least that’s their plan until the magic moment Jack puts a quarter in Joy’s slot machine and hits a $3 million jackpot. (And I’d like to find the Vegas slot machine that delivers a maximum payoff without playing more than one quarter. But I digress.)

Up until that point, “What Happens in Vegas” has borrowed — to use the polite term — from a variety of wacky meet-cute romantic comedies.

As soon as Jack and Joy start squabbling over who gets the jackpot, however, the movie shifts to more specific borrowing: from “Seinfeld” and “Curb Your Enthusiasm” creator Larry David’s 1998 comedy “Sour Grapes,” about two cousins squabbling over how to split an Atlantic City slot jackpot.

Suddenly, Jack and Joy’s routine annulment becomes a more complicated legal maneuver — especially when a traditionalist judge (played, and it’s hardly a stretch, by smirky Dennis Miller) sentences them to “six months hard marriage,” after which they can split the disputed winnings. Unless, of course, one of them bails, forfeiting the cash.

At which time “What Happens in Vegas” metamorphoses into “How to Lose a Guy in 10 Days,” with uptight Joy struggling to retain her edge in the midst of Jack’s disaster-area bachelor pad and Jack plotting ever more devious ways to gross her out. All while trying to maintain the illusion of a happy marriage for the sake of his family and her demanding boss (Dennis Farina, in ace corporate-shark mode).

No jackpots will be awarded, of course, to those who realize what it takes Jack and Joy the entire movie to realize: that he’s just the guy to cure her no-fun workaholic tendencies; she’s just the girl to drag him kicking and screaming into maturity; and they’re destined to live happily ever after. That is, if they can keep themselves from killing each other before their six-month sentence is up.

It’s nothing we haven’t seen before — and won’t see again. Yet as “What Happens in Vegas” trips along, dragging itself through the connect-the-dots plot and stumbling over the sitcom-style slapstick, there’s a frustrating sense of missed opportunities and what might have been.

If only screenwriter Dana Fox (“The Wedding Date”) had decided to make her characters a bit less cartoonish and a bit more recognizably human. And if only British director Tom Vaughan had saved a bit of the rueful charm that characterized his big-screen breakthrough, the 2006 romantic comedy “Starter for Ten.”

Instead, Jack and Joy seem to revel in all the stupid and petty things they do to each other — which the movie expects those of us in the audience to forgive, even before they forgive each other.

That would be a lot easier if we were having as much fun as the movie keeps insisting they’re having.

But between Kutcher’s exaggerated comedy stylings and Diaz’s perky stridency (or should that be strident perkiness?), “What Happens in Vegas” carries about it a faint whiff of desperation, as if they’re not quite convinced of the inevitable happy ending.

Hate to break it to you, folks, but if you don’t believe it, neither will we.

Contact movie critic Carol Cling at ccling@reviewjournal.com or 702-383-0272.