Continuity mistake: Arthur finishes the last yuppie off, and he lies stone cold dead on the stairs. However, he is not lying in the same position the two times it is seen. The second time he has his left hand one step lower than the right (which was the only one visible earlier) and his knees are on the platform (in the first shot, only the tip of the shoes touch the floor). (00:33:45)
Continuity mistake: Thomas Wayne is speaking on TV. Arthur shushes his mom. In the close-up that follows, suddenly there's an extra lock of hair against his forehead. (00:38:50)
Continuity mistake: Arthur gets on stage at the improv club and has one of his laughing fits. When the camera is behind him, facing the blinding stage lights, you can see that he is choking himself with the right arm and holding the book with the left. But it was the exact opposite in the previous shot. (00:43:44)
Continuity mistake: After the gig at the comedy club, Arthur and the neighbour Sophie pass in front of a newsstand. The copy of the Examiner saying "Killer Clown On The Loose" is kept in place by a clothing pin placed diagonally, top right-to-bottom left. In the close-up when Arthur looks at it, the pin is top left-to-bottom right. (00:45:25)
Continuity mistake: The camera pans towards Arthur when is reading Penny's letter to Thomas Wayne; the items on the table (newspaper, pen) are in a different position compared to the rest of the scene. (00:48:35)
Continuity mistake: When Arthur is choking Alfred Pennyworth through the bars, in the shot when he says "Let go, let go!" you can see behind his head the flowers from the magic wand, absent in the previous views. (00:54:50)
Continuity mistake: In the theater lavatory, Arthur puts the usher jacket in the sink. Part of the jacket drapes to the side of the sink, but at the cut the cloth is entirely contained in it. (01:05:00)
Continuity mistake: After Arthur took off the stolen jacket and hat when talking to Wayne he places them in the sink, but in the next cut they disappear. (01:05:00)
Suggested correction: You don't see the sink containing the clothes anymore after he puts them down.
Continuity mistake: Thomas Wayne and Arthur Fleck are talking in the bathroom. Joaquin Phoenix's hair changes position on his forehead several times even when he does not touch it and/or shakes his head. (01:06:15)
Continuity mistake: After Arthur steals the file from the guy in Arkham he runs and the file moves from one arm to the other. (01:13:10)
Continuity mistake: In the shot when he turns the last 2 corners in the corridor before getting to the stairs, the file in Arthur's hands is facing the opposite way compared to before and after - the label should be on the inside, not the outside. (01:13:20)
Continuity mistake: When Arthur's neighbour walks on him drying himself up in her living room, the leftmost toy on the table in front of him has the shape next to the unicorn fitting the board in the front view, but in the reverse shot the piece is off the slot. (01:17:20)
Continuity mistake: Arthur is by his mother's hospital bed, smoking. Cut to a closer view ("That's the real me"), and his shoulders are in full sunlight, while he was in the shadow only a moment before. (01:20:30)
Continuity mistake: The two former coworkers ring Arthur Fleck's doorbell. The door is suddenly fully open when he lets them in, but was less than half opened when they were talking. (01:26:20)
Continuity mistake: Arthur leans against the door frame and has a creepy chat with Randall. Joaquin Phoenix's hair is plastered to his temple in a different way between shots. (01:26:30)
Continuity mistake: When Joker is dancing on the stairs he throws his cigarette. Then when the cops arrive at the top of the stairs we see him blowing smoke from the same cigarette. Then the cigarette is gone again. (01:30:40)
Suggested correction: They purposely stuck the images in a way that it repeats itself over and over again. It's intentionally made in a way of not flowing straightforward.
Continuity mistake: Murray is leaving the dressing room assigned to Arthur, but he asks "one small thing." He is holding the cup with the hand over the lid; when he leans back into the room he is holding the cup by the side. (01:36:20)
Continuity mistake: In front of the audience, Joker sits down. After awkward silence he says that it's all just as he imagined and Murray Franklin has a comeback joke. The guest to the far end of the couch has his arms crossed, which become just his fingers entwined at the cut. (01:39:20)
Continuity mistake: During the first part of the interview, Murray Franklin's hands keep changing position inconsistently holding cue cards or being flat on the desk. (01:39:25)
Continuity mistake: Leaning against the car during the riots, Joker's face paint is smeared with a tear exactly the way it was when he walked out of the subway before the Murray Franklin show. But of course it went through a lot of fixing since. (01:46:45)
