Bromosexual

Last spring Mark Duplass wrote a one-line e-mail to Josh Leonard that would eventually launch their shambling careers in gay porn all the way to a four-minute standing ovation at this year's Cannes film festival. As actor-directors, they met on the independent film circuit. Duplass's Baghead had been a hit at Sundance, and The Blair Witch Project , one of Leonard's first acting gigs, was the most successful film ever to debut in Park City.

"I sent Josh one line: 'Do you want to play best friends in a movie this summer?' " Duplass explains over drinks at an outdoor café in Los Angeles's Silver Lake neighborhood. "And Josh wrote back, 'Hell, yes! What's it about?' And I said, 'Look, don't worry about that, it's going to be great.' "

Leonard, now sitting beside him, deadpans, "Don't ever let me agree to be in a movie again before I know what it's about."

Humpday is the story of two straight longtime friends who decide to have sex with each other and film it. It starts as a joke that becomes a challenge that then evolves in surprising and sweet ways into a genuine exploration of male friendship and the shape of desire. Ben (Duplass) is newly married and settling into domestic stasis when Andrew (Leonard) shows up from Mexico with ugly gifts and a beard to give him gravitas. On his first night back Andrew meets and introduces Ben to a polyamorous lesbian couple and their friends, who tell them about the Hump! festival, an actual and ongoing amateur porn showcase in Seattle produced by the alt-weekly The Stranger . "What kind of porn would you two make?" goads one of the women, played by Humpday director Lynn Shelton. "Two straight dudes having sex," Ben says. "It's beyond gay."

"You'll get the shit boned out of you," Andrew proclaims.

"No, you'll get the shit boned out of you ," Ben fires back.

Suddenly, it's on. Starting with a drunken, improbable double dare, Humpday follows these two friends over the course of a single weekend, from wicked hangovers the morning after to Ben's searing conversation with his wife to get permission for the "art project," ending up at the shoot in a hotel room. "We knew the concept was so absurd that the movie couldn't work on just the level of gimmicky hetero male one-upmanship," Duplass says. "There had to be a reason on an emotional level so that on a pillow at night, each of these guys had each picked this project to be a symbol of something missing in their lives."

In the film's trickiest and most refreshing angle, the obstacle to overcome is not the closet door.