Continuity mistake: When Paulie and the others are in prison and preparing dinner, there is a vase on the table where they will eventually eat dinner. The vase is filled with fresh basil at the beginning of this scene but disappears and re-appears throughout the scene.
Continuity mistake: In the scene when Spider is killed by Tommy, Jimmy is with his arms wide open just the instant before Tommy pulls the trigger. But in the next shot, when Tommy fires the gun, Jimmy is with his arms down.
Continuity mistake: In the scene near the end, when the FBI agent is explaining the Witness Protection Program to Henry and Karen, the hemline of Karen's dress changes from one shot to the next. First it's down low on her calf, then it's up by her knee, then it's down again, then up, then down again.
Continuity mistake: In the scene where Tommy shoots Spider in the foot, we hear 7 gunshots from a S&W Model 36 5-shot .38 revolver. [The first gun, not the Colt 45 he kills Spider with later.]
Continuity mistake: When Tommy kills Stacks he shoots him once in the back of the dome, then cracks Carbone's castanets about the coffee. Then it cuts to a slo-mo reprise of the whacking with a Henry voice over and Tommy shoots 6 times.
Continuity mistake: When we see the close-up of Tommy pulling the ice pick out of Morrie's head, there's lots of blood on the ice pick. But in the next shot, there's no blood on the ice pick. The next shot is a little quick and blurry, but we can still easily see the ice pick's silver when it should be red.
Continuity mistake: After Karen has been with her girlfriends, she is talking to Henry about what is going to happen if he gets killed, at that point Henry is folding his pants by the closet, when the camera angle switches he is suddenly very quick on his knees in front of Karen.
Continuity mistake: When Henry and his girlfriend enter the Copacabana avoiding waiting in the line, their way through the catacombs of the nightclub is prolonged artificially because they exit the kitchen by the same door they entered it. The scenery is changed a bit by moving some racks and a curtain but you can tell it's the same because they pass the same firehose on the wall twice.
Continuity mistake: When Karen is at the the Hostess party, and Jimmy Conway's wife is talking about Jeanie's family, if you look at the lady she's applying make up to, she crosses begins to herself twice. One when the camera is one her and Jimmy's wife, then again when the camera is just on her.
Continuity mistake: Paul and Jimmy go over to Henry's girlfriend's place with Henry, and she leaves to get cigarettes. Paul is talking to Henry about having to go back to his wife, and when they sit down, the camera goes on Henry and you can see a Jewish necklace. But later when the camera goes back to Henry, it's a necklace of a cross. (01:16:15 - 01:16:50)
Continuity mistake: When Henry beats the neighbor kid and then passes the gun to Karen, her knit sweater is sometimes on one shoulder and sometimes on both arms.
Continuity mistake: After Tommy shoots and kills Spider, Henry sits back up and puts his hands down from covering his ears twice.