'Wedding Crashers' (R) (out of four )

Vince Vaughn fans will revel in two hours of the funnyman's ad libs, pratfalls and "oh, wows" in the new movie "Wedding Crashers."

Unfortunately for Owen Wilson, Vaughn steals the show.

Billed as a frat-boy romp, the movie is a chick flick in disguise. Think "American Pie" married to "The Wedding Planner."

VideoExtra! 'Wedding Crashers'

Trailer - 'Wedding Crashers' Clip - 'Make Me A Bicycle' Clip - 'Let's Get Out Of Here' Clip - 'I Have A Gift'

Vaughn, a big bear of a guy at 6 feet 5 inches tall, plays Jeremy Grey, a divorce mediator by day and wedding crasher on the weekend.

"You blend in by sticking out," Vaughn explained to me during an interview. "You have to figure if the guy is there and being gregarious and hugging the bride and groom, he's got to know someone," he said.

Wilson is John Beckwith, also a divorce mediator, but with hair too perfect to be a wedding crasher. When Beckwith falls in love with one of his prey, he breaks one of the crashers' cardinal rules and forces Grey to hightail it to a politician's retreat so he can woo the senator's daughter.

Vaughn and Owens are masters at ad-lib and you can tell that director David Dobkin just lets the pair run with it. In one incredibly funny scene, Vaughn shares a whiskey with Father Gibson ("Laugh In's" Henry Gibson). It's a one-sided conversation with Vaughn leading the way and milking the scene for all it's worth.

The supporting cast gives the bawdy comedy even more robust energy, including a deliciously saucy Jane Seymour as the sex-crazed senator's wife, Christopher Walken as Senator Cleary and playing his usual droll self, Isla Fisher as the redhead who beats Grey at his own game and Rachel McAdams as the woman who tames Beckwith's crashing.

Just when you think the movie can't get any funnier, there's a hysterical cameo appearance by a current king of comedy who plays the kingpin of crashers.

There are so many funny scenes in this film, it's hard to imagine what deleted or bonus scenes they'll pack into the DVD release, but knowing Wilson and Vaughn, there were some pieces left on the cutting room floor that are definitely worth seeing.

And don't think for a minute this film doesn't leave an open ending for a "Wedding Crashers 2."