Continuity mistake: In the scene when Worm and Mike go to see Gramma about Worm's debt, Gramma says, "What's the matter, Lester? You looking for a little charity?" Worm curses at Gramma and takes the toothpick out of his mouth and throws it on the floor. Gramma grabs Worm immediately and the toothpick is back in Worm's mouth.
Continuity mistake: When Mike is in the bath talking to Knish, his right hand moves around a lot. Whenever Mike is seen from behind, his hand is on the marble column next to him, but when he is seen from the front, both his hands are in his coat pockets. Back and forth, through the entire scene.
Continuity mistake: In the second to last scene of the movie where Mike is playing heads-up with Teddy KGB, there is an inconsistency in the bets that are made. Previously in the movie, the black chips are shown to be worth $100 each. When Mike raises $1000 straight, he places 20 chips down, a total of $2000.
Factual error: After Mike sets Worm up at the club and leaves, Worm asks for $2,000 of debt in Mike's name to sit at what was moments before identified as a $20/$40 limit game. The woman is next seen putting four rows of green $25 chips into a chip rack. A $20/$40 game would never be played with $25 chips because this denomination makes it very difficult or impossible to bet the required amount, at least without $5 chips to make change on every bet, which would be extremely tedious. Rather, $20/$40 games are played with $20 chips made specifically for games of those stakes, and they are usually yellow in color.