Dirty secret: Raunch-fest has its funny moments

For all the rudeness and crudeness he splatters across the screen, Kevin Smith is at heart a moralist – albeit a moralist with a potty mouth.

His latest, “Zack and Miri Make a Porno,” is a raunch-heavy comedy about two childhood friends who decide to make a dirty movie together and maybe fall in love along the way.

He's more convincing with the raunch than the love, and that's OK. Like all Smith movies, “Zack and Miri” is uneven, but when it's funny (and that's often) it's a scream.

The titular characters (Seth Rogen, Elizabeth Banks) met in kindergarten and have been platonic roomies since graduating from high school a decade ago. They live in a ratty rented house in icy Pittsburgh, work at a franchise coffee shop and … and that's about it. They're classic underachievers.

This fact is driven home when they attend a class reunion. Everybody else seems to have grown up, while Zack and Miri are still living lives of prolonged adolescence. There's a very funny scene in which Miri throws herself at the old classmate she worshipped from afar (Brandon Routh of “Superman Returns”), only to find he's come to the party with his boyfriend (Justin Long).

Things get worse when Zack and Miri find their water and electricity turned off for unpaid bills. Zack comes up with a plan. If everyone is fascinated by porn, wouldn't they be even more fascinated if they knew the people in the porn?

Zack convinces a henpecked co-worker (Craig Robinson) to put the money he was saving for a big-screen TV into their production. For his cash, the sex-starved guy gets a producer credit and the opportunity to interview “talent” for the movie.

Initially, they plan a sci-fi spoof called “Star Whores.” When their sets and costumes vanish along with the condemned warehouse they've rented, the ragtag cineastes decide to film at night in the coffee shop where Zack pulls lattes.

“Zack and Miri” works best in the 40 minutes leading up to the actual porn shoot, thanks to Smith's hilarious dialogue and the pitch-perfect performances of Rogen and Banks.

Rogen gives yet another variation on the pudgy slacker he has already portrayed so memorably in “Knocked Up” and “The Pineapple Express.” But like Bill Murray, he's developed a stock character we don't easily tire of. The guy may have the best comic timing in the movies today, and since he's frequently the butt of his own self-deprecating delivery, there's not a trace of arrogance or snideness.

Banks has got comedy chops to spare. Here, she deftly projects Miri's blend of sexiness and insecurity.

Smith is judicious in his use of nudity (naked women are many things, but funny is not usually one of them), but a fairly high squirm factor remains. He's much better at verbal humor than the visual kind. But at heart he's just an old-fashioned romantic.