Tailored Role
Arthur Fleck’s, AKA the Joker’s, role was created with Joaquin Pheonix in mind. In late 2017, Pheonix received the movie script and even had his own mother take a look and help him decide if to take the role or not.
Batman: The Killing Joke
The movie’s storyline was based on the graphic novel, Batman: The Killing Joke. Otherwise, the movie didn’t reference any other Batman comics. The director, Todd Phillips, co-wrote the screenplay with Scott Silver in 2016, and by early 2018, they had Joaquin Pheonix signed on as the lead character.