Continuity mistake: When Willie and Joey are pointing their guns at Delores in Vince's office, they count to three, waiting for the other to shoot first. In the close-up shot, Willie's gun is closer to Delores' head than it was in the previous wide shot.
Continuity mistake: The number of nuns in the choir changes between when Mary Clarence joins, the later casino scenes, and the end concert for the Pope. At the start, there are over 20, and by the ending, there are about 12-15.
Continuity mistake: When Deloris is on TV, we see her lift a stuffed rabbit to try and hide her face, she then gives it to Mary Robert and lifts the kid to her face but when Eddie says "I'm gonna kill her. I'm gonna kill her myself", if you look on the TV, you can see her doing the exact same thing again.