Joaquin Phoenix's Joker one of the greatest performances I ever seen: Jessica Chastain

Seems like Jessica Chastain has joined the 'Joker' fan clan as the actor feels the movie is "one of the greatest pieces of acting" she ever saw!

Even more, Chastain was just left "shook" by Joaquin Phoenix's performance.

"Mouth was dropped open in the theatre as it played. It left me shook," Chastain tweeted.

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Phoenix's October release set the cash registers ringing at the box office as the film raked in over USD 856 million worldwide, and even became the highest-grossing R-rated film of all time.

Not only did it ruled the box office, but also bagged the Golden Lion award and an eight-minute standing ovation at the Venice Film Festival in late August before its premiere at the Toronto International Film Festival.

While speaking at the film's Toronto International Film Festival premiere in September, Phoenix said playing the Joker was "one of the greatest experiences of [his] career."

"I mean honestly, it wasn't an easy decision at first. I didn't f--ing know. I didn't. But then there was something that was drawing me toward it. It just evolved as we worked together. It started becoming something more than I anticipated. It was one of the greatest experiences of my career," People quoted the actor as saying.