Rob Brown has joined the cast of Joseph Gordon-Levitt’s untitled directorial debut.Gordon-Levitt will play a Don Juan type who sets out to become a less selfish person. Brown will play Gordon-Levitt’s best friend in the pic. Scarlett Johansson, Julianne Moore and Tony Danza also star. Gordon-Levitt also penned the script and Nicolas Chartier’s Voltage Pictures will finance the film. Ram Bergman will produce. He is repped by WME and Industry Entertainment.