Lady Gaga Talks Joker: Folie À Deux's 'Rough and Tough Energy' in Exclusive Behind-the-Scenes Video

Lady Gaga wowed Joaquin Phoenix and director Todd Phillips on the set of Joker: Folie À Deux.

In a new featurette about the making of Joker: Folie À Deux, exclusive to PEOPLE, Gaga, 38, reveals she was fascinated by the world filmmaker Phillips, 53, and Phoenix, 49, created in 2019's Joker when she saw an early screening of the movie.

"It was a very special experience," the Oscar winner says in the clip. "I had never seen a world created like that before."

Fans have been waiting for Gaga's upcoming performance as Lee, a version of the popular D.C. comics character Harley Quinn — otherwise portrayed by Margot Robbie on the big screen in recent years — since the A Star Is Born actress confirmed her casting back in August 2022. As Phillips and Phoenix say in the new featurette, Gaga was more than ready for the challenging part.

"She easily slipped into that world. It's not like she's trying to be Harley Quinn from the comic books; she's Lee in this world," Phillips says of Gaga's performance. Phoenix, meanwhile, was impressed with Gaga's work ethic on set.

"I found her to be without ego and had such a fierce determination. She would get right in with us," he says of Gaga, whose character finds love with Phoenix's own Arthur Fleck in the sequel. "She understood that there had to be a rawness to the character. There's not a lot of actors that are comfortable working in that way."

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The new behind-the-scenes clip comes after Folie À Deux made its world premiere at the Venice Film Festival on Sept. 4. Gaga, Phoenix and Phillips were all on hand in Italy to debut the long-awaited sequel. Aside from its leading actors, the film also costars Brendan Gleeson, Catherine Keener and Zazie Beetz, who reprises her role from the 2019 original.

"It brought out all of that rough and tough energy and how big these dreams were, and how far they would fall," Gaga adds of her performance in the video.

"Joker: Folie À Deux finds Arthur Fleck institutionalized at Arkham awaiting trial for his crimes as Joker," reads an official synopsis for the upcoming movie. "While struggling with his dual identity, Arthur not only stumbles upon true love, but also finds the music that's always been inside him."

Joker: Folie À Deux is in theaters Oct. 4.