During Roth's birthday party, the pattern on his shirt changes. Due to weather difficulties, the two minute scene took over a week to shoot and the original shirt was lost at some point. The production designer attempted to recreate it by drawing an approximation of the pattern onto a plain shirt, but it didn't quite match.
Shortly after the assassination attempt on Michael in his bedroom, he meets alone in a room with Tom Hagen. They sit at an empty table. After talking for a few minutes, Michael offers Tom a glass of Courvoisier, from a bottle which has randomly materialized on the table.
At the end of the movie in the flashback, they talk about the Japanese attack on Pearl Harbor happening "on Pop's birthday". The Pearl Harbor attacks were on December 7, but according to his tombstone, in The Godfather (1972), Vito's date of birth is April 29.
When Signor Roberto visits Vito at work, Signor Roberto counts money on Vito's desk. The arrangement of the money changes between shots.
The carpet that Clemenza starts to roll up before he is interrupted by the knock at the door, is much smaller than the one he and Vito are shown carrying into the building in the next scene.
If the gold telephone was in fact solid gold, it would've been so much heavier than the way it seemed, by how easily it was passed along the table.
Upon his arrival on Ellis Island, a migration official sees that young Vito Andolini comes from Corleone, Sicily, and decides to change his name to Corleone. While it is a popular urban legend, migration officials did not unilaterally make such radical changes to a person's surname. At worst, they might misspell it if they only heard the name instead of seeing it written. Many immigrants did choose to change their names, either the to simplify the spelling or Anglicize them. In the novel, Vito chooses to take the name Corleone to honor his home town.
When receiving payment from Vito Corleone, Don Fanucci removes the spoon after stirring his espresso. There is no coffee on the spoon; it is dry. This indicates the demitasse is empty.
The Feast of San Rocco is on August 19, yet the crowd is dressed for cold weather in overcoats, etc.
In the beginning, it's shown that young Vito's name was changed at Ellis Island from Andolini to Corleone. Although this is a widely held belief, the fact is that no names were ever changed by officials at Ellis Island, who only confirmed information on the arriving ships' manifest. Any name changes were made by the immigrants themselves.
In his later scenes, Don Fanucci has slash marks on his neck/throat area that weren't there earlier. (This is because of a deleted scene in which Fanucci is jumped on the streets by a group of young thugs, who slash him. The scene doesn't appear in the regular cut of the film, but does appear in the edit of The Godfather: A Novel for Television (1977), and as a deleted scene in the DVD set.)
When Vito Corleone arrives at Ellis Island, he was marked with a circled X (historically X was a sign for a mental illness), not because he was suspected to have smallpox, but because he was a nine year old who did not speak. Even deaf people at the time were frequently labeled as "retarded" simply because they did not speak.
In Michael's office during Anthony's communion party, it appears the Senator sets down his bottle of pills on the table after he takes them and never picks it up. However, although very brief, immediately after setting down the drink used to take the pills, you can see the Senator motion for his pills. After returning from a shot of Michael, the Senator is then seen closing his right pocket, presumably with the pills inside.)
The supposedly dead prostitute can be seen breathing by the movement of the white sheets.
Vito Corleone's birthday is revealed to be December 7th; however, his tombstone in The Godfather states his birth date to be April 28, 1887.
When they are passing around the solid gold telephone, most of the people show how heavy it is. And yet, when Michael Corleone, and Hyman Roth handle and pass the telephone, it appears light as a feather and no indication is given as to how truly heavy a solid gold telephone is. Thus destroying the illusion that it is real.
At approximately 13:30 mark, four or five of the children sitting at the kids table put their fingers in their ears in anticipation of the fanfare and drum roll that was about to happen; indicating this was not the first take these little actors had to endure.
In the opening scene when Vito's mother touches Paolo's body, his hand visibly moves. His fingers curl up and that is something a dead body just can't do. He is also seen obviously breathing in the subsequent moments.
Batista is speaking English to the room full of his American friends and investors, yet his translator is translating his conversation in Spanish. It should have been the opposite; Batista speaking in Spanish and the translation in English.
During the end credits of The Godfather Epic one of the credits is misspelled "The Godather"
When Michael visits Miami in 1958 many high-rise hotels are visible in the background. In reality a great majority of high rise hotels in Miami were built in late 1970s and early 1980s. In 1950 there were hardly any high rise hotels in Miami.
Michael's bodyguard Al Neri kills Johnny Ola on the balcony of Hyman Roth's suite. There is a doctor and several other people present in Roth's bedroom and later some ambulance people arrive to take Roth to the hospital. No one seems to notice a dead man on the balcony, no one wonders where Ola has gone, and at the hospital, Roth is left in a relatively unguarded room.
You can see the lamination separation in the vent window of the red and black 1958 Ford Michael drives to Roth's house; this would not happen on a then-new car.
When young Vito arrives in New York and the Statue of Liberty is shown, the patina on the statue is clearly bright green. The patina on Lady Liberty would not have been completely developed in 1901. At the time, the patina was covering most of the statue, starting with the torch, arm, head and torso, but not the entire length of the statue's dress as shown in the film. It should have been covered in a patchy patina from the waist down, with a primarily brown color.
The text in the funeral scene says Vito was nine years old in 1901, but according to his headstone in The Godfather (1972) he was born in 1887 and would have been 14 years old.
The American flags visible in the 1917 street carnival should have 48 stars, not 50.
Michael comes home to Lake Tahoe, after Christmas, his car passes through the gate, and the gate is closed by one of his security team. On the gate is an "ADT" security monitoring sign, which was introduced in 1974.
On the driver's side of the windshield of the red and black automobile that Michael Corleone drives to Hyman Roth's home in Miami, there is a 1970s Florida Vehicle Inspection sticker.
After the attempted assassination on Michael, Tom and Rocco are overlooking the discovery of the dead bodies in the water. When Rocco turns away from Tom to ask where Michael is, his lips do not move while the soundtrack says "Where's Mike?".
When Vito and Genco go to the theatre, and watch the 'Senza Mama' show, the singer's voice is clearly out of sync with the words of the song.
When the mule used to sneak young Vito past Don Ciccio's men walks through the piazza, we hear the clacking of its hooves. However, the piazza seems to be covered in dirt rather than stone.
When Vito gets the 50 dollars from both Clemenza and Tessio, Tessio wishes him good luck. His lip movements do not match his dialogue.
When Michael is having cake at Roth's birthday party, he is heard speaking while the visual shows him about to eat a forkful of cake.
When Vito is driving and Fanucci hops onto the car, another car passes between the camera and Vito's car - Coppola and the camera can be seen reflected in the car's window.
During the Cuban rebel uprising scene, a store is looted while Michael Corleone makes his escape. Something is stuck to the camera lens and can be seen as a silhouette on the screen.
When Fredo gets to the hotel in Havana, Cuba, the Dominican Republic flag is clearly visible on the flag pole.
During the final scene flashback, they are talking about the attack on Pearl Harbor happening on "Pop's birthday". It is also revealed that this led Michael to enlist in the army "this morning". Since the attack happened in Pearl Harbor at 8AM Hawaiian time, news of the attack couldn't have reached New York before 1PM.
As Michael and his men head to Florida, there is an external shot of the front of the train they are traveling on. It is clearly a Union Pacific Railroad train with the bright yellow orange diesel engine with the UP emblem, blue wings with a red and blue shield. Their coverage is entirely west of the Mississippi River.
When traveling into New York Harbor for the first time, young Vito's boat is traveling south, away from Ellis Island toward the ocean.
When young Vito is quarantined, we are led to believe that he is still on Ellis Island. As he looks out the window, the shot from outside shows the reflection of the Statue of Liberty. By that reflection (the front of the Statue) Vito would have to be on Governors Island.
The Chairman of the Senate Investigating Committee points out 1947 as the year Michael Corleone kills Virgil Sollozzo and Captain McCloskey; but in The Godfather (1972) it was established as happening in 1945.
When Michael reads his prepared statement to the Senate committee he states that he received the Navy Cross for his wartime service; however, in The Godfather (1972) he wears the ribbon for the Silver Star instead.
Michael is asked at the senate hearing if he coordinated the murder of the heads of the five families in New York in 1950. Since Michael stood accused of being one of those five people, they should have instead asked him if he planned the murder of the other four bosses. Also, the murder of the other family heads took place in 1954 or 1955.
At the 14 minute mark Senator Geary asks Michael and Kay to stand up. Instead of saying Mike, Kay please stand up he says "Mike, Pat (his own character's name), Kay, please stand up".
While it could be argued that "A real professional would not have made that mistake" of shooting a person in the left side of the chest if the heart (which is really dead center) was the intended target, it has to be noted that this was the gunman's first kill and therefore hardly a seasoned "professional" by a log way yet. Also, the heart residing slightly to the left was a very public and commonly held belief to anyone but maybe the medical profession, certainly at the time of the early 1900's. If anything, that continues to be a common misconception to this very day.