Following a formula is fine when making a movie -- formulas work, which is why they become formulas -- but you have to come up with new twists.

"What Happens in Vegas" does not come up with any new twists. It doesn't even try. As a result, this would-be comedy winds up inducing a massive, movie-long sense of déj? vu.

Writer Dana Fox, whose previous script was the similarly formulaic "The Wedding Date," simply pulled out Standard Formula No. 1 (not even No. 2): A pretty male character and a pretty female character think they hate each other, have to spend time together and then realize they actually love each other after all.

In Standard Story Line No. 1 (not even No. 2), the two are actually married to each other. So while they think they are wrong for each other, we know they actually belong together -- if for no reason other than they are both so pretty.

Cameron Diaz plays uptight career-woman Joy, who is dumped by her bland fiancé. Ashton Kutcher plays slacker permanent-bachelor Jack, who is fired by his own father (Treat Williams, of all people, in a decidedly secondary role).

Both decide to lick their wounds in Las Vegas, the tourism bureau of which must have had a hand in this flick's financing.

The two meet in a way that is supposed to be cute, and is not. They spend some time together drinking, and after a night of drunken debauchery wake up married.

They plan to get a simple and quick annulment, but then fate intervenes and they win a $3 million jackpot when Jack puts Joy's quarter in a slot machine.

We're supposed to think, "That shows they're meant for each other," but all we think is "They found a slot machine that still accepts coins in Las Vegas?"

The money complicates the annulment, for some reason. The state Supreme Court judge who hears their case -- yes, their annulment is heard in the state Supreme Court -- decides that they have to spend six months together trying to make the marriage work before he will grant the annulment.

The judge is played by Dennis Miller and his name is R.D. Whopper. Were the filmmakers even trying?

It will not surprise you in the least to learn that each character has a best friend. Jack's is a worse version of himself, played by Rob Corddry. Joy's is a somewhat better version of herself, played by Lake Bell. In comedies such as this, the best friends typically get all the good lines, but the good lines here are few, indeed.

Joy's friend tells Jack's friend, "If I could make someone dead with my mind, it would be you," but that's about as good as it gets.

The biggest problem with "What Happens in Vegas" is in the premise itself. The characters agree to stay together only to collect the jackpot, and they try to sabotage the relationship so that each can collect the whole thing himself.

It's hard to root for the two to fall in love when we think of them as horrible, horrible people.