The final scenes of the film were filmed in the Opera House "Teatro Massimo" in Palermo. But this Opera House was closed in 1974 to complete renovations required by updated safety regulations, and it remained closed for twenty-three years, finally re-opening on 12 May 1997, so a playing of the "Cavalleria Rusticana" was not possible at the beginning of the 1980s in that Opera House.
There are numerous errors in the use of Latin by priests in the film. In Saint Patrick's where Michael Corleone is honored by the Church, the presiding clergyman pronounces the Latin word et ("and") as "ay", rhyming with "day", as if it were French. It is in fact pronounced like it's spelled, to rhyme with "wet" and "pet." Later when Cardinal Lamberto (later Pope John Paul I) absolves Michael Corleone, he ends with the standard "in the name of the Father," etc., in Latin. But he wraps it up saying "et Spiritus Sanctus." The correct Latin is "et Spiritus Sancti." But Spiritus is not a nominative, it's the genitive (possessive) singular of a fourth declension noun, and the correct form of the adjective is Sancti. Of course these very mistakes won't be noticed by many viewers, but they will be noticed by anybody who took first year Latin and/or had any training in the Church.
Vincent points out to his cousin that Vito Corleone started as a lowly delivery boy at the Genco Olive Oil Company. In fact, Vito was its founder. It is possible, however, that Vincent was thinking of Vito's tenure at the Abbandando Grocery Store, where he in fact was a delivery boy. It was where he met his friend and future partner Genco Abbandando, after whom their joint venture was named.
At the beginning of the movie Vincent gets in a scuffle with security at the party being held for Michael. Vincent's coat gets knocked off his arm but in the next shot it's there again. This happens a few times and when Vincent walks away the coat is back on his arm.
The camera the photographer uses at the party changes make
and model between shots. Also, the cord connecting the lens to the flash equipment appears and disappears between shots. Then when he is done with the last shot, he completely disappears along with the tripod and camera from the staircase as the kids run past.
When Michael visits Archbishop Gilday, the Archbishop has a lit cigarette cupped in his hand. While telling of the bank's woes and his need for Michael's help, another priest offers the Archbishop a cigarette and lights it for him. The first cigarette has disappeared, yet there has not been enough time for, nor any action indicating onscreen, the Archbishop has extinguished the first cigarette.
When Kay is on the steps about to get into the car in Sicily, Michael can be seen removing his cap through the windshield. Then, after she gets into the car, Michael turns around and again removes his cap.
At [1:21:00] When Don Altobello is visiting Michael in the hospital and, at the end of their conversation, they agree to meet in Cicily, they shake hands like sports' teammates do but in the next shot, right afterward, they look like as if they were shaking hands in the businessmen formal way.
When Vincent pulls his gun to shoot Zasa, his horse is faced to the left. He aims his gun to his left, toward the camera, crossing his right arm in front of himself. He then shoots, but now the horse is facing right, and he shoots toward his right, and the camera, with his arm out straight.
The Opera Cavalleria Rusticana is shown out of chronological order. The prologue is shown first (Anthony singing backstage), followed by a scene near the end. The procession scene shown next, is actually in the middle of the opera. Then the conclusion is shown.
When Cardinal Lamberto hears Michael Corleone's confession, he is not wearing the purple stole all priests wear during the sacrament. There is no reason why he wouldn't have one, since all priests carry one on their person at all times in case of emergency (such as giving absolution during last rites).
In the Opera some scenes take place in an empty box with unused stacked chairs. In a presumably sold out show there would be no unused boxes and even if so, the box would have been prepared, because it can be looked over by the boxes on the other side, as we see the boxes with the audience.
Already in Sicily, when Michael's daughter runs away due to her father advice to quit her relation with Vincent. Tony tries to soften the situation finally saying "She'll understand about Joey". When in fact he should have said Vincent.
Although the details of Pope John Paul I and his death in the film are not always consistent with those of the real Pope John Paul I, this is not a factual error, as this film is only presenting a fictional story partially (and loosely) based on true events.
When Corleone allows himself to be shaved a towel is placed over his left shoulder. A second later it is shown on his right shoulder. However when the towel is placed on his shoulder he is seen reflected in his shaving mirror and the shot switches to a non reflected shot so it is actually on his right shoulder to start with.
In an early scene, in Michael's office, a picture can be seen of Vito and Michael, from the scene in the first movie, where Michael and Vito are talking privately about the upcoming Barzini meeting. There was nobody else there, so who took that closeup picture that's now framed on the wall?
Many times newspaper headlines are shown describing events in the film. However, the clearly legible articles underneath the headlines are obviously unrelated to the headlines. In one case, a WSJ headline "article" appears to have been lifted directly from a computer instruction manual!
When the assassins find Frederick Keinszig and begin to subdue him; he reaches for his gun on top of the table of stolen money. As he struggles, one of the top bills gets moved to reveal that the stacks of money are mostly just blank pieces of paper.
The scenes where Michael advises his daughter Mary against seeing Vincent, and the one where he gives Anthony the car drawing seem to have been shot in sequence. That is noticeable because Anthony is wearing the same clothes and in the first scene (with Mary) Anthony has the car drawing in his hand.
The goof items below may give away important plot points.
Right after Mary gets shot a frame of Vincent screaming enraged is shown a few steps below where he had just killed the assassin, next frame Michael clasps a motionless Mary and Vincent is seen calmly strolling upstairs in the background as you continue to hear his enraged cries. Seconds after there's a shot of what appears to be a supposedly dead twin bodyguard checking on the assassin, and a somehow blood-stained suit worn by Vincent, who apparently jumped 20 steps in 3 seconds and now looks despaired.
After Mary has been shot, Michael puts his head in his hands. There is no blood on his shirt, even though he stood right by her at the time of the shot, which was heading in his direction, and afterwards he cradled her body in his arms. The camera cuts away to Kay cradling Mary's body, then cuts back to Michael. Blood has now appeared prominently on his shirt.
Both twin bodyguards are killed during the opera performance. After the final assassination attempt outside the opera house, one of the twins can be seen near Vincenzo frisking the body of the slain assassin.
No less than two shots of the dead Don Tomassino in the casket were done with very obvious rear projection, most evident by frozen film grain around the casket. Meanwhile, Michael (to the left of the casket) is surrounded by a very natural film grain.