Lady Gaga in Talks to Play Harley Quinn in Joker Musical Sequel Opposite Joaquin Phoenix

Eamonn M. McCormack/Getty Images; Steve Granitz/WireImage

Paging Dr. Quinzel!

Lady Gaga is in talks to play Harley Quinn, opposite Joaquin Phoenix, in the upcoming follow-up to 2019's Joker — which is also set to be a musical, PEOPLE confirms.

The Hollywood Reporter was the first to share the news, reporting that Gaga's Harley would exist "in a different DC universe" than the one played by Margot Robbie in Suicide Squad (2016), Birds of Prey (2020) and The Suicide Squad (2020).

While plot and character details are still unknown, Harley — originally known as Dr. Harleen Quinzel — is villain Joker's love interest/sidekick in several iterations of the Batman story, and met the sinister prankster while serving as his psychiatrist at Gotham City's Arkham Asylum.

With a working title of Joker: Folie à Deux, the film will see Todd Phillips return as director, as well as co-writer alongside Scott Silver.

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Niko Tavernise/Warner Bros. Entertainment Joaquin Phoenix in Joker (2019)

RELATED: Joaquin Phoenix Pictured Reading Script for Joker Sequel – and It Even Has a Title!

Phillips, 51 alluded last week that a Joker sequel was in pre-production on Instagram.

The two-part post opened with the red cover of a script titled Joker: Folie à Deux. The binder was dated May 18 and featured his name next to that of Silver, 57, with whom he also co-wrote the first Joker screenplay.

A second shot showed Phoenix — who won the Academy Award for Best Actor in 2020 for his role as Arthur Fleck and his alter ego in the first film — casually reading the script on a couch while smoking a cigarette.

While Deadline reported at the time that Phoenix, 47, had yet to officially confirm that he'll pick up the lipstick again, the post teased the possibility that the actor would once again step into the supervillain's shoes.

Folie à Deux, which references a delusion or mental illness shared by two people, also suggests that Joker may also team up with another supervillain – possibly his sometime-girlfriend Harley.

RELATED VIDEO: Joker Breaks October Box-Office Record with $93.5 Million

Phillips' original Joker broke box-office records as the first R-rated movie to hit the $1 billion mark in 2019. The movie reimagined the DC character's narrative and earned 12 Oscar nominations, including Best Picture, Best Director and Best Adapted Screenplay.

In addition to Phoenix's win, composer Hildur Guðnadóttir took home Best Original Score.

Amidst the positive buzz, however, the movie also generated controversy, with people concerned about whether its depiction of violence would incite copycats. Additionally, it featured a song by convicted pedophile Gary Glitter — though it was later reported that he would not receive royalties from the song "Rock and Roll (Part 2)" being used in the movie.

Responding to the backlash, Phoenix said in part in 2019, "Well, I think that, for most of us, you're able to tell the difference between right and wrong."

He added at a Joker press conference, according to IGN, "Those that aren't are capable of interpreting anything in the way that they may want to."