New York Film Fest: 'Inherent Vice' Cast Reveals What It's Like to Work With Joaquin Phoenix

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Joaquin Phoenix on the 'Inherent Vice' red carpet Saturday night

Plus, Jena Malone explains how she first met Paul Thomas Anderson 11 years ago at L.A. burger shop The Apple Pan

Joaquin Phoenix isn't the most media-accessible actor.

At the Saturday press conference for his latest movie Inherent Vice, Phoenix joined the cast and director Paul Thomas Anderson onstage but remained silent.

Read more 'Inherent Vice': Film Review

Later that night, he predictably walked past reporters on the red carpet ahead of Inherent Vice's world premiere at the New York Film Festival.

So what's the seemingly standoffish, three-time Oscar nominee actually like on set?

"He is the nicest person, he genuinely is, down to his core. He knows everyone's names. He's such a class act on set. He treats everyone with such respect and he's just a wonderful human being. … He has no airs and graces, no ego and he just is," Pretty Little Liars' Sasha Pieterse told The Hollywood Reporter of her Inherent Vice co-star.

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Jena Malone, who has a small but significant role in Inherent Vice as a recovering heroin addict, echoed those sentiments.

"He's one of the most generous actors I've ever worked with and so talented," Malone said, adding that working with Phoenix is a transformative experience. "You get to kind of become a wild animal and everything is new and innate and fun again and that's a pretty incredible thing."

Phoenix also taught his onscreen partner, played by Jordan Christian Hearn, a thing or two.

Hearn, who appears in many scenes as the sidekick to Phoenix's scruffy P.I. in Anderson's trippy adaptation of Thomas Pynchon's novel, said he took after his co-star by keeping Pynchon's book on hand.

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"We always had our books with us, and we were highlighting, and we know the lines in the script and we also know the lines in the book, so if there was any improv or anything like that, we could hammer something out that was still true to the story," Hearn said.

The film's star-studded cast also includes Martin ShortReese Witherspoon, Owen Wilson, Benicio Del Toro, Josh Brolin and Anderson's real-life partner Maya Rudolph. In the film, Phoenix's Doc Sportello begins investigating the disappearance of the current boyfriend of his ex-girlfriend Shasta Fay Hepworth (Katherine Waterston), but the search turns into a long, strange trip in which Doc encounters a number of crazy characters as the case grows larger and more complex.

Read more New York Film Fest: Paul Thomas Anderson's Ensemble on the Chaotic Logic of 'Inherent Vice'

Waterston was in awe while working with Anderson, calling it, "The best thing that ever happened to me in my life."

"There was a lot of pinching going on. I was pinching myself a lot. … Paul is my favorite filmmaker. The only filmmaker whose movies I go to on opening weekend, without fail," she said. "Two years ago, if I had been asked to write down my fantasy scenario, it would be this."

Short also said he jumped at the chance to work with whom he considers "the most interesting filmmaker out there," but that, once on-set, he was surprised by Anderson's laid-back attitude.

"I hadn't met him until like wardrobe and I expected him to be more of a brooding auteur. He's just like a dude who's making a movie. He's very loose," Short said. "You know, Maya Rudolph I knew from SNL, and you knew she'd have to be with a cool guy."

Watch more The First Trailer for 'Inherent Vice' Has Arrived

Hearn and Pieterse also talked about Anderson's chill nature on set, both saying that they arrived on set to find the filmmaker sitting on the floor barefoot.

Speaking of laid-back, Malone revealed that she had a very low-key encounter with Anderson 11 years ago.

"It's funny. We met actually at Apple Pan, at this little burger shop in L.A., and I didn't know it was him! He was all scruffy and had a beard, and we were talking about films," she explained. "Then when we met again for the film, he was like, 'You remember when we met at Apple Pan' and … I did but I kind of didn't know. So it's all full-circle, it's pretty amazing."