The 47-year-old star won the Oscar for Best Actor in 2020 for his dark portrayal of the comic book villain in the origins movie about the party clown Arthur Fleck's descent from troubled loner and failing comedian to psychotic murderer.
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Director Phillips shared a post on Instagram of the script, along with a black and white photograph of Phoenix sitting reading it in his pyjamas with a cigarette hanging from his mouth.
From the Instagram of @/ToddPhillips. pic.twitter.com/iYGmj0LFzB
— WarnerBrosUK (@WarnerBrosUK) June 8, 2022
The cover reveals the follow-up film is titled Joker: Folie a Deux, which is French for 'madness for two'.
In 2019 Phillips denied he was in talks to make a sequel to the critically acclaimed Joker, saying: "Here’s the real truth about a sequel. While Joaquin and I have talked about it, and while touring the world with Warner Bros executives — going to Toronto, and Venice, and other places — of course, we’re sitting at dinner and they’re saying: ‘So, have you thought about?’
“But, talking about contracts, there’s not a contract for us to even write a sequel, we’ve never approached Joaquin to be in a sequel."
But Phoenix admitted he was keen to continue exploring the character as soon as work on the first film began.
He said: “In the second or third week of shooting, I was like: ‘Todd, can you start working on a sequel? There’s way too much to explore.’
“It was kind of in jest — but not really.”
Joker quickly became the most profitable comic movie ever made, earning over $1bn off a $60m budget.
The movie received huge critical acclaim and multiple awards including the Best Actor Bafta, Golden Globe and Screen Actors Guild accolades for Phoenix. It also won him his first Academy Award, following three previous nominations.
The film noir explored the creation of the DC Comics character's villainous alter ego and also documented how a young Bruce Wayne was left orphaned in riots by the disgruntled people of Gotham City.
But The Batman featured a different incarnation of the Joker, played by Eternals star Barry Keoghan.
Watch: Joker told the origins story of the comicbook villain