Lady Gaga had "no ego" while shooting 'Joker: Foile À Deux'

Joaquin, 49, has now told in a behind-the-scenes featurette film put out ahead of the 'Joker' sequel's cinema release: "I found (Gaga) to be without ego and had such a fierce determination. She would get right in with us.

"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."

'A Star is Born' actress Gaga adds in the film about making the 'Joker' follow-up: "It was a very special experience. I had never seen a world created like that before."

"It brought out all of that rough and tough energy and how big these dreams were, and how far they would fall."

'Folie À Deux' had its world premiere at the Venice Film Festival on 4 September 4, with Gaga, Joaquin and its director Todd Phillips, 53, all in attendance.

He gushed about Gaga: "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."

A synopsis for the 'Joker' sequel says: "'Joker: Folie À Deux' finds Arthur Fleck institutionalized at Arkham awaiting trial for his crimes as Joker.

"While struggling with his dual identity, Arthur not only stumbles upon true love, but also finds the music that's always been inside him."

The film also stars Brendan Gleeson, Catherine Keener and Zazie Beetz, who reprises her role as Sophie Dumond from the 2019 original.