The 44-year-old Phoenix has already been winning raves from critics for his performance in this deeply unsettling new film, which is set to open next month.
Buzz on Phoenix’s performance has been through the roof since the Joker world premiered at the Venice Film Festival, where the movie took home the prestigious Golden Lion.
According to a recent New York Times report, the actor “lost his composure on the set, sometimes to the bafflement of his co-stars.”
The report quoted Joker co-writer and director Todd Phillips as saying: “In the middle of the scene, he’ll just walk away and walk out.”
“And the poor other actor thinks it’s them and it was never them — it was always him, and he just wasn’t feeling it… If he goes on Jimmy Kimmel and walks off after two minutes, I’d be like, ‘That’s my boy.'”
Phoenix did not, however, ever walked out on his most esteemed co-star Robert De Niro, who plays a late-night talk show host in the film.
“Joaquin was very intense in what he was doing, as it should be, as he should be,” De Niro said.
Todd Phillips and Joaquin Phoenix worked together for months before the production started on Joker.
They got into heated discussions about every little detail of the character, down to how much he should weigh. When it came down to it, Phoenix wanted to play Arthur Fleck at a normal weight, while Phillips wanted the character to be super skinny.
In the end, the director won and Phoenix dropped 52 pounds to get into character.
He also learned how to apply his own clown makeup and started a journal, which he filled with one-liners and jokes that appear in the movie.
Joker is in theaters on October 3.