Oona Chaplin, Sam Worthington and Stephen Lang chat with ET’s Denny Directo about their film, ‘Avatar: Fire and Ash,’ which hits theaters on Dec. 19. Series newcomer Oona explains how she came up with her character’s villainous strut and why James Cameron reminds her of her grandfather, the late great Charlie Chaplin. Plus, Sam Worthington reveals how fatherhood influenced his approach with Jake Sully.