Revealing mistake: In the scene where Lorraine Bracco points a revolver at Ray Liotta's head, after Ray Liotta turns the tables and now points the gun at Lorraine Bracco as he gets up and walks away you can see Ray Liotta steps on Lorraine Bracco's hand and she opens her mouth wide like shes screaming but it must have been cut from the audio, as Ray walks off camera his expression changes to show that he knew he had accidentally stepped on his co-workers hand.
Factual error: If you look at the band playing in the Regal Club the night the boy's mother first visits, the night where they first bring on the donkey, you'll notice that the drum kit used by the drummer in the band is, from what we can see, a 1980's Pearl kit, far too modern. (00:39:00)