Warner Bros and DC's Joker is helmed by The Hangover trilogy director Todd Phillips and Joaquin Phoenix stars as the iconic comic-book bad guy. Robert De Niro might play a talk show host who is "somehow instrumental in the Joker’s origin."
One of the most famous villains in pop culture, The Joker's charm lies in the mystery itself. Over-explaining the Clown Prince of Crime would deprive the character of his frightening charisma. I, for one, do not give a flying fig about how he got his scars.
Unmoored from the comic-book lore, the Joker origin movie starring Joaquin Phoenix is likely going to use the bare essentials of what makes the character such a terrifying villain. It would likely be a character-driven story instead of a loud comic-book film.
Warner Bros. has greenlit a standalone Joker origin film which will star Joaquin Phoenix. Another Joker standalone with Jared Leto in the lead is already in the works. Phoenix's film has been given the moderate budget range of 55 million dollars.