Currently, only four actors have been confirmed so far for the cast, which will steadily grow larger as production begins. The main stars of the film will be Joaquin Phoenix, who's reprising his role of the Joker from Joker, and Lady Gaga, who will be giving us her take on Harley Quinn, as Margot Robbie and Kaley Cuoco are most well-known for playing the character.
In addition, Brendan Gleeson and Catherine Keener were just recently announced to have joined the cast, though both of their roles are currently undisclosed to the public. Gleeson is well-known for his past roles in Gangs of New York, Harry Potter, and Into the Storm (2009); he's also appearing in the highly-anticipated film, The Banshees of Inisherin, which is set to premiere on October 21, 2022. Keener is most famous for her performances in Being John Malkovich and Capote, having just recently starred in The Adam Project, which was released in 2022.
And though he's not a part of the cast, director Todd Phillips will be directing this Joker sequel.
As the production trucks along, more and more rumors and leaks will come to light, but as of right now, the only unconfirmed rumor is that Zazie Beetz might be returning to her role as Sophie Dumond, the Joker's neighbor in Joker.