Joker: Folie à Deux must replace one missing character. Joker was released to commercial and critical acclaim, with Todd Phillip's direction and Joaquin Phoenix's acting receiving high praise. Phoenix's portrayal of Arthur Fleck earned him an Academy Award for Best Actor in 2020. Although originally conceptualized as a stand-alone film, a Joker sequel was announced in June 2022 by director Todd Phillips with a release date of October 4 2024. Later that month, Lady Gaga was confirmed to play Harley Quinn, a psychiatrist that falls in love with Arthur.
https://screenrant.com/joker-2-robert-de-niro-replace-actor/