Lady Gaga, Joaquin Phoenix, director Todd Phillips talk 'Joker' sequel

"Joker: Folie à Deux" is almost here and ahead of its premiere, the stars of the film -- Lady Gaga and Joaquin Phoenix -- opened up on some of the challenges they faced while making the highly anticipated sequel.

"We were under a microscope from the very beginning, and then we bring Lady Gaga in," director Todd Phillips told "Good Morning America" in an interview. "But it’s kind of the 'why' we do what we do, right? To take risks."

Since the news of the sequel to Phillips’ 2019 "Joker" film was announced, audiences have been excited to see what’s in store for the protagonist, Arthur Fleck (Phoenix), who, in the first film, is introduced as a failed clown and aspiring stand-up comedian in Gotham City.

He transforms into the Joker, a criminal mastermind, after several moments in the film show how he’s isolated, bullied and disregarded by society. The role earned Phoenix an Academy Award for best actor in 2020.

Phoenix returns for the sequel, with Gaga joining as Harley Quinn.

Gaga said Phoenix’s performance in the first film made her want to be part of "Joker: Folie à Deux."

"That was what really interested me in being a part of this one because I loved Arthur so much," she said. "Like, who would be the love in his life?"

While on the set of the film, which incorporates renditions of iconic songs, Phoenix said that Gaga was the one who suggested that they sing some of the songs live.

"When we first started, I did not want anything to be spontaneous," Phoenix said. "I wanted to sound as good as possible, and Stef, Gaga said, ‘We should do them live.’"

"I was like, ‘Yeah, well, it’s easy for you to say, ‘cause this is what you do,’" he said, adding that Gaga made him "feel comfortable" about singing.

Gaga called Phoenix’s natural voice "more compelling than any lip-syncing would ever be."

In terms of playing Quinn, Gaga said it was "freeing."

"I was able to put some things of myself in her that maybe I’ve always been embarrassed of or things that are really private," the Academy Award winner said. "When I first saw the film, I remember thinking, ‘Oh,’ like ‘that’s in there.’ That part of me that I want no one to know about – she’s kind of so uncomfortable."

"She’s on the edge," she added. "There’s definitely been times in my life where I’ve felt that way."

"Joker: Folie à Deux" arrives in theaters on Oct. 4.