Continuity mistake: When Johnny Friendly is threatening Charlie about keeping Terry from testifying, they are seated at a table across from each other. There is a bottle of alcohol in front of Charlie. In most of the scenes of Charlie behind the bottle, the label can be seen in full. In a couple of scenes, the bottle is turned to the right and only shows a partial label. Charlie was obviously not handling the bottle.
Continuity mistake: During the start of the famous "I coulda been a contender" scene, watch Terry's head. When he tells Charlie that "it was you", his head is tilted to the left. In the next shot, it's tilted to the right.
Continuity mistake: In the taxicab scene when Charley threatens Terry with a gun, it is obviously a toy or a starter pistol that shoots blanks. When Terry appears in the Bar scene with what is supposed to be the same gun, it has become a very real .38 snub nose Detective Special.