Lady Gaga and Joaquin Phoenix appeared on Good Morning America on September 27th who sat down with Chris Connely to discuss their highly anticipated film ''Joker: Folie à Deux.'' Along with director Todd Phillips, they opened up about the challenges of creating the sequel. Gaga, who stars as Harley Quinn, talked about how the depth of Arthur Fleck (Phoenix) attracted her to the project.

Phoenix returns for the sequel, with Gaga joining as Harley Quinn. "That was what really interested me in being a part of this one because I loved Arthur so much," Gaga said. "Like, who would be the love in his life?"

"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."

While on the set of the film, which incorporates renditions of iconic songs, Phoenix said, "When we first started, I did not want anything to be spontaneous," Phoenix said. "I wanted to sound as good as possible, and ... Gaga said, ‘We should do them live.’" Gaga also called Phoenix’s natural voice "more compelling than any lip-synching would ever be."

Watch the extended interview that was later aired on ABC's Nightline.