Continuity mistake: When Michael enters the room where he sees Kay looking nostalgically at the old photos, he is carrying and offers to her pieces of cake from a cake that hasn't even been cut yet. They are the exact size and dimension of the cake slices that will betaken from the celebration cake which is not cut until several scenes later.
Factual error: In the parade scene with Joey Zasa, they are having a raffle where they can win a Cadillac Eldorado. On the car a sign reads "Win THIS 1979 CADILLAC Diesel." The mistake: This a not a 1979 Cadillac Eldorado, it's a 1980 Cadillac Eldorado. The difference is the grill and a light under the headlights. The grill for the 1979 model has 14 spaces between the vertical metal beams, the 1980 model has 18 spaces between the vertical metal beams. Also the 1980 model has orange lights under the headlights, 1979 model has no such colour. Even though these two models are almost identical, there is a small difference in appearance. (01:17:55)
Continuity mistake: At Michael's celebration there is a scene of a family photograph taken on the stairs of his home. When the photographer is taking the picture of the family, you can see that the camera he is using is a Sinar P1. But when the scene's angle is reversed, you see the front of the camera, and it is a completely different one - a Toyo-View G.Louise Rose
Continuity mistake: When Mary is hit at the end of the film and Kay screams, Vincent looks up and shouts "No!" and the scene cuts back to Michael holding Mary, as we hear Vincent continue his line ("Mary!") but then Vincent appears behind Michael and Mary, walking slowly up the steps, hair slicked back, gun in hand, mouth closed as his line is still being delivered, with no pause ("Mary! No!"). The next cut shows Vincent back at the bottom of the stairs near the priests, with his hair mussed up. And the poor editing continues - when the camera pans out following Michael's scream, we can see Vincent slowly walking up the steps behind Michael, and this is the same shot as before from a different angle.
Continuity mistake: During the scene that takes place at the party were Connie is singing the song about the instruments, Vincent Mancini and his mother can be seen arriving to find out their names have not been listed to attend. The shot switches back to Connie singing, and Vincent's mother can be seen at a table enjoying the song and festivities. It then cuts back to the entry hall where Vincent begins to shove people around, and his mom is still standing there looking upset that they have not been admitted to the affair.
Revealing mistake: Several newspaper spins show Michael Corleone in the headline, but a screen shot reveals body copy that is unrelated or outdated. For example, the headline dated 1979 has copy referring to events occurring in the 1990's. Another has body copy with instructions from a software manual.
Factual error: The opening scene shows the 1979 NYC skyline with the World Financial Center (now known as Brookfield Place) visible, which wasn't built at that time.