-By Ethan Alter

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Fairly or not, mumblecore—the name that's come to stand for any super-low-budget American film involving aimless twenty-somethings who sit around talking endlessly about their lives and relationships—has frequently been treated by both the studio and independent film industries as the cinematic equivalent of summer stock. And, to be honest, the movies themselves haven't done a lot to counter that impression. Simply (some might say indifferently) directed and populated largely by novice actors, most mumblecore productions look and feel more like home movies than feature films. Small wonder, then, that the genre has mostly been confined to film festivals—specifically Austin's annual South by Southwest shindig, which seems to be mumblecore's unofficial epicenter—and the few titles that distributors have picked up never play outside the art-house circuit.

Now along comes Lynn Shelton's Humpday, which has the potential to become the first mumblecore flick to cross over into the mainstream. In terms of its production values, the film isn't noticeably any different from the rest of its brethren; it's still shot vérité-style with handheld cameras and features lots of overlapping conversations that sound entirely improvised. But Humpday has something most mumblecore movies don't: a great commercial hook, as well as a breakout performance from a young actor with actual Hollywood experience—that would be Joshua Leonard, whose previous credits include The Blair Witch Project, Live from Baghdad and a guest spot on "CSI: Miami."

In standard studio-pitch parlance, Humpday is probably best described as I Love You, Man meets Zack and Miri Make a Porno. Mark Duplass (a mumblecore veteran who has acted in such movies as Hannah Takes the Stairs and co-directed The Puffy Chair and Baghead with his brother, Jay) takes the Paul Rudd role as Ben, a former party-hearty type who has since gone the family route, marrying the lovely Anna (Alycia Delmore), getting a steady job and preparing for the pitter-patter of little feet. But late one night his past returns to haunt him in the form of his former partner-in-crime Andrew (Leonard), a professional bon vivant back stateside after an extended sojourn south of the border. Andrew's presence puts Ben on the defensive as he tries to justify his new lifestyle to his buddy and, in a strange way, himself. Their casual rivalry leads to lots of "can-you-top-this" macho posturing that ultimately results in the duo agreeing to enter a local amateur porn contest with a video that shows them having sex…with each other.

If Humpday were a studio-made film, this is the point at which it would turn into a broad comedy a la I Now Pronounce You Chuck and Larry, where the main characters "played gay" while always winking at the audience to let them know they were still walking the straight and narrow. Fortunately, Shelton is more interested in exploring behavior than scoring easy laughs. Male insecurity and competitiveness has rarely been depicted this effectively onscreen and Leonard and Duplass deserve credit for not holding back out of fear of not being "likeable" enough. Leonard in particular deftly portrays Andrew as a person worthy of envy and ridicule in equal measure. And while the bulk of the movie understandably focuses on the guys, Delmore has a number of memorable moments where she reveals Anna to be more open-minded and daring than either her husband or his big-talking best friend.

Humpday's only significant flaw is that it builds to a finale that can't help but feel anticlimactic. Once Ben and Andrew enter the hotel room where they plan to get busy in front of the camera, the situation can really only play out two ways and neither one would be wholly satisfying. At least Shelton avoids ending the film on a too-pat resolution, allowing the men to go their separate ways still wrestling with the emotions their brief encounter has stirred up. If more mumblecore movies took their cue from Humpday, the genre might finally start getting some respect.