Mark David Duplass (born December 7, 1976) is an American filmmaker, actor, writer, and musician. With his brother Jay Duplass, he started the film production company Duplass Brothers Productions in 1996, for which they wrote and directed The Puffy Chair (2005), Baghead (2008), Cyrus (2010), Jeff, Who Lives at Home (2011), and The Do-Deca-Pentathlon (2012).