Having finished the first ''Austin Powers,'' director Roach got horny for an early draft of ''Meet the Parents'': ''I told Universal, 'This is the funniest thing I've read. I don't want to change any of it.' They said, 'We think it can be better.' I think what they were politely saying was 'We think it can be better directed by somebody else.'''

After the script got passed to DreamWorks, which became a coproducer, Steven Spielberg considered directing Jim Carrey as the nervous dude who clashes with his intended's dad. When that lineup fizzled, Roach says he ''pounded everybody involved, 'Please, let me have it back.''' By then, the ''Powers'' flick had hit franchise pay dirt, and Roach got the job.

Though he was keen to cast Stiller as the bumbling beau, the actor had doubts. ''The first draft I read must have been from when they were thinking Jim, because it was much more physically oriented,'' Stiller recalls. ''Like, the toilet's overflowing, and my character sits on it to stop it. He uses himself as a human, uh, y'know, plug. I read that and said, No way I'm gonna be funny doing that.'' But once De Niro signed on as dad, Stiller had ''no choice'' but to play Greg Focker, male nurse.

Meantime, a third-act crisis -- how to resolve the dad/ boyfriend tussle believably? -- made Roach as nervous as the father of a bride. ''My next film, I don't want things unraveling a week before the shoot,'' he says. Rewriting by Hamburg continued after production started, but the stars and director wound up relying heavily on improv for the finale (including a Stiller outburst on a plane). ''I was adamant that Greg have more backbone,'' Stiller says. ''Jay had to mediate and say, 'This is the way I want to shoot it. Trust it.''' GOOD SIGN One look at De Niro's narrowed eyes in the trailer and you're laughing. THEN AGAIN This won't be the American Assembly for Men in Nursing's favorite movie.