'Joker 2' is a musical starring Joaquin Phoenix and Lady Gaga — here's everything we know Joaquin Phoenix and Lady Gaga star as Arthur Fleck and Harley Quinn, respectively, in Todd Phillips' sequel to "Joker." Here's what to expect. https://www.businessinsider.com/joker-2-folie-a-deux-cast-trailer-plot-release-date-2024-4