Why so serious? Joaquin Phoenix, Lady Gaga to co-star in 2024 Joker sequel

Joaquin Phoenix will reprise his role as the Joker in a sequel to the 2019 Oscar-winning psychological thriller, a spokesperson for film distributor Warner Bros. said on Wednesday. Lady Gaga confirmed in a separate Instagram post that she will co-star.

Joker: Folie à Deux is set for release in theatres on Oct. 4, 2024

Joaquin Phoenix wins the Oscar for Best Actor for his role in Joker at the 92nd Academy Awards in February 2020. Phoenix will reprise the same role in a 2024 sequel, according to a spokesperson for Warner Bros. (Mario Anzuoni/Reuters)

A motion picture sequel to the Oscar-winning psychological thriller Joker, based on one of the world's best known comic book villains, is set for release in theatres on Oct. 4, 2024, a spokesperson for film distributor Warner Bros. said on Wednesday.

Joker: Folie à Deux will star Joaquin Phoenix reprising his role as the title character, according to the studio spokesperson. His performance in the original 2019 film, depicting an origin story for the arch enemy of DC Comics' superhero Batman, earned him an Academy Award for best actor.

Joker, which in addition to Phoenix's win was nominated for best picture at the Oscars and won for best original score, was directed and produced by Todd Phillips, who co-wrote the script with Scott Silver.

The story charted the psychological descent of the film's protagonist, a failed party clown and wannabe comedian Arthur Fleck, and the social forces that transformed him from a dejected loner into a cold-blooded killer who inspires a wave of violence in the fictional metropolis of Gotham City.

Lady Gaga confirms that she will co-star

Phoenix in a key scene from the 2019 blockbuster Joker. (YouTube)

No further details about the sequel were immediately made available by Warner Bros.

Lady Gaga, who was reportedly set to play Joker's co-conspirator, Harley Quinn, in the sequel, confirmed as much in an Instagram post on Thursday. Hollywood trade publication Variety also reported that the new production will be a musical.

Phoenix, 47, known for playing brooding or emotionally troubled characters, was widely acclaimed for a performance that many critics hailed as "chilling" and "disturbing."

He was the second performer to earn an Academy Award for playing the Joker, following in the footsteps of Heath Ledger, who posthumously won the Oscar for best supporting actor for his 2008 rendition of the character in The Dark Knight.