8 Actors Who Were Confused While Filming Movie Scenes

There's a scene in Joker where Joaquin Phoenix's Arthur Fleck attends a stand-up comedy show, hoping to learn a thing or two from professional comedians.

During one set, Fleck - who has a medical disorder that causes him to laugh uncontrollably - consistently laughs at inappropriate times, finding things funny that nobody else in the room seems amused by.

The comedian performing that set was played by real-life comedian Gary Gulman, and hilariously, he didn't know that it was Phoenix who was responsible for those random bursts of laughter.

In fact - as he informed Collider - Gulman was confused and irritated by the noise, thinking that a random extra was messing the scene up:

"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. 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 [Philips, director] about maybe getting the guy not to laugh so loud, I realized that it was Joaquin Phoenix. 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."

Quite why nobody told him that Phoenix would be acting weirdly during the scene is anyone's guess, but perhaps Philips thought that keeping Gulman in the dark would add to the authenticity of the sequence in some way.