EXCLUSIVE: Sean Penn is in negotiations to play a small but pivotal supporting role in 20th Century Fox’s remake of The Secret Life Of Walter Mitty, the comedy that Ben Stiller is directing, with Stiller playing the title role. Stiller plays the timid magazine photo manager who goes off on an escapade to find a missing negative. Kristen Wiig, Adam Scott, Shirley MacLaine and Patton Oswalt also star. Penn most recently wrapped The Gangster Squad, playing L.A. gangster Mickey Cohen in the Ruben Fleischer-directed period cop drama at Warner Bros. He’ll next be seen in the Paolo Sorrentino-directed This Must Be The Place and is being courted by Alejandro Gonzalez Inarritu for The Revenant. He’s repped by CAA.