Revealing mistake: When the new Pope is announced, the New York Times headline is shown, and 'Copyright 1990 The New York Times' is visible. The event took place in 1979.
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.
Continuity mistake: When Kay visits Michael in hospital the oxygen tube is sometimes running under his shoulder, sometimes across the pillow. (01:07:55)
Continuity mistake: When Mary comes to Vincent's club and they talk while he is cooking gnocchi, the salt container and the pans on the shelf keep changing positions. (01:11:50)
Continuity mistake: When Michael, Anthony and Mary are walking along a wall, Anthony is holding a sheet of paper which he is studying at the beginning of the first shot in the scene. The paper is the picture of Michael in his limousine that Anthony drew as a child (and is seen in Godfather Part II). However, Anthony isn't given this picture until later in the film. Notice that they're wearing the same clothes in both scenes. Clearly a much longer scene was cut into two parts, and the second half is seen first. (01:31:35 - 01:51:55)
Other mistake: The close up of the Wall Street Journal mentioning Immobiliare seems to have operating instructions for a Windows program under the headline. The newspapers previous to this appearance also have a headline pasted onto another news topic altogether. The same happens later with the newspapers covering cleansing actions of the new pope. These papers date from March 27, 1980, although the events are supposed to take place in 1979. (00:41:42 - 02:00:00)
Continuity mistake: After their walk through the town of Corleone Michael and Kay sit at the dining table and talk. The knot of Michael's scarf keeps moving from the middle to the side and back. (01:55:55)
Continuity mistake: When Mary asks her father if she is just a front of the foundation she holds her arms to her chest. When the camera angle changes her arms are crossed on the table. Also her hair falls over her shoulder totally differently. (00:44:15)
Continuity mistake: When Vincent is not allowed to join the party in Michael's honor he starts a fight with the security guy. While they are wrestling the coat over Vincent's arm flies off, but reappears and again disappears in the following shots. (00:06:45)
Continuity mistake: When the train with Kay arrives at Bagheria the sun is shining onto the platform, but when she gets off the sunlight is gone. (01:45:20)
Continuity mistake: When Joey Zasa comes to Michael to complain about Vincent, Michael asks Al Neri to get him. Al leaves and we hear the door close behind him. Then Vincent comes, accompanied by his aunt, but Al is nowhere in the picture. But when Vincent does a Mike Tyson on Zasa's ear both Vincent's thug Squigilaro and Al come to separate the two opponents. (00:23:45 - 00:27:30)
Visible crew/equipment: In the scene where Joey Zaza is murdered, one of his henchmen gets gunned down with a shotgun. Just before the blast hits him, the side of one of the wooden street stalls magically changes to a breakaway so he can crash through it dramatically, instead of just slumping down against it as he would in reality.
Deliberate mistake: When the heads of the families assemble in the Palazzo Azzuro in Atlantic City and get attacked from a helicopter the rotors make the glasses on the table shake and the piles of fruit in the bowls collapse. As the Palazzo looks like quite a solid building this effect is a bit exaggerated. (00:59:35)
Continuity mistake: When Calo assassinates Don Lucchesi, he grabs the Don's glasses and stabs him in the upper chest about three inches below the collar of his shirt, yet later, when Lucchesi is shown slumped in his chair and bleeding, the glasses are seen sticking out of his neck above the collar.
Continuity mistake: When Michael and the archbishop discuss the deficit of the Vatican bank, a folder on the table in front of Michael is only there when the camera is on Michael but not when it's on the bishop. (00:39:05)
Continuity mistake: In the scene where the Corleone's are travelling to the house in Bagheria they are in 3 cars. When they arrive at the house they are being escorted by 2 motorbikes not there in the previous scene. (01:21:30)
Continuity mistake: Mosca, the assassin, in preparing to shoot Michael Corleone at the opera house, is installing the telescope on his rifle backwards. Later, when seen aiming the rifle, it is installed correctly, but is a different telescope.
Visible crew/equipment: When Zasa's two henchmen try to kill Vincent and he shoots the second one through the hand, you see a bulge in the guy's palm just before it explodes to create a 'hole'. (00:34:30)
Other mistake: Before Joey Zasa is murdered, an altar boy in the parade (on the left side of the screen) can't help but stare at the camera all the time.
Continuity mistake: In the sequence of the attack on all the Dons in Atlantic City, three Dons can be seen being shot in the beginning of the shootout, a few moments later, you can see the same three Dons being shot again. (01:00:00)
Answer: Michael is trying to divest the family of all ties to organized crime. Internazionale Immobiliare is an international real estate concern and owning it would legitimize the family. Michael is attempting to buy out the Vatican's 25% of the shares in it to gain controlling interest, but the other families either want in on the deal or want to steal it out from under him, forcing him back into his old criminal ways.
Captain Defenestrator