Continuity mistake: In the kitchen scene where Bugsy has made a birthday cake for his daughter but has missed her party because guests arrived, the camera shot changes from Bugsy to his wife and back a couple of times. When the shot is from behind Bugsy, there is smoke coming from the birthday cake candles. When from behind his wife, there is no smoke.
Continuity mistake: Guy Bannister brutally pistol-whips Jack Martin (Jack Lemmon) across the face several times as a warning never to discuss his inside knowledge of the assassination. In the next shot of Jack on the floor, he has no blood or any visible abrasions whatsoever on his face. (00:14:04)