Now, according to The Hollywood Reporter, Academy Award winner Robert De Niro is in talks to join Joaquin Phoenix for the film, according to The Hollywood Reporter.
The film will be produced by Emma Tillinger Koskoff and executive produced by Richard Baratta and begins production later this year.
Warner Bros. is also reportedly in development on a separate Joker feature film which would star Jared Leto as the villain, reprising his role from Suicide Squad.
The Joker origin movie that will stand apart from the DC Extended Universe is making big strides in coming together, officially getting the greenlight earlier this month and setting a release date.