After going to Mia's flat, Vincent finds her lying on the floor dead, her eyes still open. He has his hand on the back of her head turning it up to look at her. As he begins to rest her head back on the ground her eyes twitch twice.
When there is a man talking to Vincent at 1:12, he shoots his gun from under the table and there are 3 bullet holes, when it cuts back after showing the man hit by the bullets, there are no holes in the table.
During the fight between the two prisoners, one prisoner is wearing red jail house outfit then seen wearing a blue jail house outfit.
When they begin to put Petey into the trunk, the tail lights are off. During the close up, the tail lights are on. Then during the far shot of the closing of the trunk, the tail lights are on.
While Sonny and Jack were driving to get the money to Vincent and Biggs, their limousine had a sunroof; but upon arrival, their sunroof was no longer there.
The Butcher states there are 207 bones in the body, when there are in fact only 206 bones.
Russel, the diamond exchange guy, says that he was approached to sell uncut diamonds, but earlier in the film when we see the diamonds they were very clearly cut.
The whole movie looks to take place the middle of winter, not spring or fall. Yet when mob boss Biggs is talking to Tony (not credited) while they are drowning the Russian, they talked about the game and balls and strikes. While it can get cold at the beginning of baseball season and the end, the movie was obviously set in dead winter, when no baseball is being played.
When the bullet is removed from Sonny's shoulder, he instantly becomes pain-free and reverts to full health, suffering no impaired movements throughout the rest of the film. Quite a miraculous recovery.
As Joey is preparing to remove the bullet, he warns Sonny against touching the wound with dirty hands, yet proceeds without cleaning or gloving his own hands.