Though they're happy to accept studio writing assignments, the siblings often go off script with their own films, relying on lots of actor improvisation. ''There's something to me more exciting about the electricity and the surprise,'' Duplass says. ''That's why I'm willing to accept a moment where the camera had to zoom in to catch the frame right and might shake around, and the sound might be a little off.''
Those rough edges have led to an unfortunate term for their style of intimate, fly-on-the-wall moviemaking: mumblecore. ''I full-on hate it,'' Duplass says of the label, which has become a clumsy catchall for a wide variety of low-budget films from directors like Shelton (Humpday), Joe Swanberg (Alexander the Last), and Lena Dunham (Tiny Furniture). ''I would hate for an audience member to hear that [a movie] is called 'mumblecore' and say to themselves, 'What is that? That sounds pretentious and actually somewhat pejorative, and I'm gonna stay at home.' That would really bum me out.''
Staying at home apparently isn't in Duplass' nature. It may seem strange for a filmmaker to take on so much acting work, but he says being a performer for hire is his ''anti-burnout medicine.'' ''Writing and directing a movie is like being a parent. There's nothing more rewarding to me than the movies that Jay and I make as your children are. But they're a lot of f---ing work, and sometimes you just feel like, 'I don't know if I can do this anymore,''' he says. ''Acting in a movie's like being a grandparent. I come in and we do a bunch of circus activities, and have some candy, and stay up late, and have fun and then I go home and leave the children there.'' It's kind of a backward metaphor for a guy at the start of his career, but that's Mark Duplass' style.