Lady Gaga in early negotiations to play Harley Quinn in 'Joker 2'

According to Varitey, after Phillips posted the screenplay cover on Instagram on June 7, rumours that Harley Quinn will star in the film began to circulate. The subtitle, Folie a Deux, refers to a shared delusional disease, and Quinn, a character first introduced for 'Batman: The Animated Series' in the early 1990s, has been Joker's only actual partner - aside from Batman.

Making 'Joker 2' a musical is another brave move by Phillips, who reframed the Dark Knight's number one villain as a loner anti-hero and hit gold at the movie office (with $1 billion in worldwide grosses) and the Oscars (with 12 nominations and two wins) when he did so. Joaquin Phoenix won the best actor for his portrayal of the Joker, aka Arthur Fleck; he's poised to reprise his role, though his contract hasn't been finalised yet.

All other information about 'Folie a Deux' has been kept under wraps, so it's unclear whether Gaga will also contribute music to the project, although it's a fair guess that she will. Phillips collaborated with Gaga as one of the producers on the 2018 film 'A Star Is Born,' which earned Gaga an Oscar nomination for best actress and an Oscar victory for original song.Bradley Cooper, the star and director of that film, was also a producer on 'Joker,' but it's unknown how much of a role he'll have in 'Folie a Deux.'

For Warner Bros., Harley Quinn has proven to be a long-lasting character. Margot Robbie has performed the part three times, in 2016's 'Suicide Squad," 2020's "Birds of Prey,' and 2021's 'The Suicide Squad,' and Kaley Cuoco voices the character on HBO's 'Harley Quinn,' which will air Season 3 later this year, as reported by Variety.

Phillips' 'Joker' films, on the other hand, live in their own fictional universe from the rest of DC's offerings, much as how Robert Pattinson's 'The Batman' can coexist with Michael Keaton's version of the character, who will appear in 2023's 'The Flash.' (ANI)