The Farrelly brothers know that constructing a comedy around a man who woos another woman on his honeymoon can leave some of the audience asking, "What?"

That's the premise of "The Heartbreak Kid," starring Ben Stiller as an indecisive single guy named Eddie who marries in haste. Eddie, fearing Lila (Malin Akerman) is his last chance at love, marriage and happiness, proposes after only a week but regrets the decision while they're honeymooning in Mexico. That's where he meets Miranda (Michelle Monaghan), who may be his soulmate.

Scheduled for an Oct. 5 release, it's an update of the 1972 comedy starring Charles Grodin as the groom, Jeannie Berlin as his annoying wife who holes up in their Miami Beach hotel room after getting sunburned, and Cybill Shepherd as the Minnesota blonde who catches his eye.

"My brother, Peter, and I definitely tried to put our stamp on the original story," Bobby Farrelly said in a recent phone call. "We made some substantial changes and we put in our brand of comedy but, at its core, we stayed close to the original where a man on his honeymoon falls for another woman.

"We saved some of the more memorable scenes from the original, like the sunburn scene and the way he starts telling small lies to her and then they get out of control and he starts telling bigger lies as he goes, and then when he tries to break it off -- we call it the pecan pie scene -- at the restaurant and it's difficult for him to do and people keep interrupting him."

Lila was a composite of former girlfriends writ large.

"All of our jokes in all of our movies are loosely based on our own lives," Farrelly said, because the things that happen to them or close friends are funnier than anything they could create.

For Lila, they "magnified" things that annoyed them about former girlfriends. They also felt it was important for the audience to understand what drives Eddie.

"The first girl is just drop-dead gorgeous -- the one he marries -- but she turns out to be a little nuttier than he thought. You didn't feel so bad for her, because you knew she was going to be OK, anyway, so it's not like he's kicking her to the curb and trading up. He just happened to meet this other girl who was a better fit for him. She's also pretty but she's more, like, soulful and more in tune with what he is ... and so hopefully the audience recognizes that."

That wasn't necessarily the case with the Grodin-Shepherd match in the original, directed by Elaine May and rated PG.

The update is rated R, and Farrelly thinks it will be a good fit for the fall. "I think we'll find the audience we're looking for, which would be more like college kids, young adults, couples, a little bit older because there is some very sexually charged comedy in here that brings it into R-rated territory."

The Farrellys were ahead of the R-rated comedy curve with "There's Something About Mary," which helped pave the way for such recent hits as "The 40-Year-Old Virgin" and "Knocked Up."

"If our names can get any way linked to 'Knocked Up' and '40-Year-Old Virgin,' I'm happy about it because those are really good movies," but with obviously adult subject matter.

"To make a movie like that and then say, 'Yeah, but let's make it for 13-year-old boys because they're the ones at the mall watching movies,' that's a mistake. So if we helped to at least be true to where the comedy is in the story, I'm happy about that."

But the R rating isn't the secret to success. "It has to be an otherwise sweet story that has R-rated antics in it."

And if the audience isn't laughing or getting it, the brothers will know long before the Fandango figures are in.

"We do extensive screening of the movies. We really rely on the audience to teach us a lot about what we're doing right and what we're doing wrong."

The brothers pick a spot in the theater so they can hear the laughter and watch any shifting in the seats if a scene proves long or sluggish.

While they may work with stars such as Stiller, Jack Black, Matt Damon and Jim Carrey, they're anonymous.

"We're very nondescript guys."