Comedian Gary Gulman struggled through several takes of his scene during filming because of Phoenix's performance.

Stand-up comedian Gary Gulman has been having an extraordinary month thanks to the premiere of his HBO comedy special “The Great Depresh” and his cameo in Warner Bros.’ blockbuster comic book drama “Joker.” Gulman appears in the Todd Phillips-directed film as a stand-up comedian during a scene in which Joaquin Phoenix’s Arthur Fleck attends a show and jots down notes while listening to Gulman’s set. Arthur laughs at inappropriate times because he suffers from Pseudobulbar affect (PBA), which causes uncontrollable laughing outbursts. Gulman recently told Collider he was unaware about this part of Phoenix’s character, so he was understandably distracted while filming his scene.

“The one thing I will say that was a little bit irritating is that when I was running through my set, there were all these extras, and they’d clearly been told that I was doing well, so they were laughing and enthusiastic,” Gullman said. And there was one extra who was so enthusiastic in his laughter that it was throwing off my timing.”

“He was just laughing too loud, and right when I was about to say something to Todd about maybe getting the guy not to laugh so loud, I realised that it was Joaquin Phoenix,” Gullman continued. “It’s my best ‘Joker’ story. I can’t believe it took me six takes to figure out that the man with the really bizarre laugh was the Joker.”

Phoenix revealed before the October release of “Joker” that he studied real victims of PLC (Pathological Laughter or Crying) to help craft his laugh as heard in the movie. “I saw videos showing people suffering from pathological laughter, a mental illness that makes mimicry uncontrollable,” the actor told Italian magazine Il Vernerdi . “The incredibly unfunny disease causes involuntary laughter or crying, usually separate from any kind of conventional trigger.”

Since opening October 4, “Joker” has broken several box office records and currently stands as the highest grossing R-rated movie ever released worldwide with over $850 million and counting (unadjusted for inflation). Phoenix’s performance has earned widespread critical acclaim, and he’s widely expected to land an Oscar nomination for Best Actor.

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