When Susan Alexander Kane is doing the jigsaw puzzle by the fireplace, in the first wide shot it's clear that the puzzle is almost complete, but in the subsequent close-up the puzzle has hardly been started.
At the first time on the opera house stage, just before Susan begins to sing, two men pass carrying a litter behind her twice.
The jigsaw puzzle that Susan is putting together changes considerably between the shot where Kane walks into the large room and asks her what she's doing and the next cut, where Kane is standing in front of the large fireplace. The amount of puzzle that she has completed increases greatly between the 2 shots.
At party to celebrate the new staff members, in the "front row" from left-to-right, men in positions 4, 5, and 6 are bald-headed, with #6 wearing a distinctive striped suit. As Kane walks in front of them, making fun of Jedediah's necktie, camera angle changes, and man formerly in position #6, has now moved down about five "positions," and is soon to be seated next to Kane.
When Kane is performing his "rooster" as a shadow show to Susan, his hands are not in the position they would be to cast the shadow as it appears.
The Russian newspaper lists Charles's first initial as C. In Russian, that letter is pronounced S. There is another letter in Russian, that looks like an upside-down lowercase h, that is pronounced CH. Either that letter, or K for the Russian form Karl, should have been used as his first initial.
One of the posters advertising Susan Alexander's opera appearance shown in the newsreel misspells her first name "Suzan".
In the beginning, Kane says, "Rosebud." The nurse enters the room after the word is spoken. The shooting script only mentions Kane and the nurse being in the room. However, within the movie itself Raymond the butler tells the reporter that he had heard Kane say "Rosebud" after the fight with Susan as well as just before he drops the snow globe, implying that what the viewer is shown in that scene is from Raymond's P.O.V.
During the breakfast table sequence, Kane refers to the President as Emily's "Uncle John." There were no presidents named "John" between Tyler (1841-5) and Kennedy. The name may have been chosen to make clear that the president in question is fictional.
During the picnic scene towards the end, Welles had to shoot against a back-projection because a location shoot was too costly and time-consuming. The stock footage used for the exterior was taken from King Kong (1933), hence on closer inspection the four birds that fly by are in fact very definite pterodactyls. RKO told Welles to take the pterodactyls out of the shot, but he liked them, and decided to keep them.
After Kane's mother signs the contract for Thatcher, she stands up and seems to walk through the table on her way back to the window. This is due to the table being moved in order to create a continuous tracking shot from the front of the set (where the table was) to the back (window).
The long dolly shot from outside the Kane house in Colorado and all the way back inside through two rooms, ending on the far side of a table, could not have been achieved with the table in place and, instead, the table had to be moved into position once the camera was past. It's an almost perfect illusion except that the hat on the table is still wobbling slightly (from the sudden movement) by the time it comes into shot.
In the aquarium, a wire holding the 'octopus' is visible.
When Leland and Bernstein are inspecting Kane's art purchases, Leland moves a statue which wobbles too quickly for it to be made of a dense stone such as marble.
In the newsreel, the announcer states how a defaulting boarder had left the deed to a supposedly worthless mine (the Colorado Lode) to Mary Kane in 1868, then begins his next sentence, "Fifty-seven years later, before a Congressional committee," as the film cuts to an old newsreel of Thatcher testifying before the committee. Fifty-seven years after 1868 would be 1925. As "talking" pictures were at best still in the experimental stage and in any case not in use in 1925, it would not be realistic that the newsreel of Thatcher testifying before Congress would have sound. Similarly, the sequence immediately following Thatcher's testimony, stated by the announcer as "that same month in Union Square", depicting the radical speaker denouncing Kane, would also not have had sound.
When Jim Gettys reveals Kane's mistress to his wife, Gettys shouts to Kane, "We've got proof! It will look bad in the papers" Looking closely, he actually said, "...It will look good in the papers..."
At the end of her interview with the reporter Thompson, Susan Alexander Kane says, "Come around sometime and tell me the story of your life," but as she says this her mouth is not moving.
When Kane shouts at Jim Gettys from the stairwell, it is clear that most of the words he is saying are not coming out of his mouth.
While standing at the large fireplace, Kane says to Susan, "I don't care to visit New York." The video of Kane's mouth movements is not synchronized with the audio.
When Kane returns from Europe, he enters the Inquirer news room and rushes towards the camera, which dollies back. At this point, and when he subsequently leaves, the dolly track is visible on the floor.
At the party scene where Kane dances with the girls, there are several shots of his reflection in the mirror. The camera shoots directly into the mirror and its silhouette can be clearly seen.
There is a camera shadow on the large doors to the Thatcher vault as Thompson enters.
When Kane and Thatcher are having a heated discussion in the newspaper office, they both suddenly stand. A shadow of the camera is then visible on Thatcher's back.
In the projection room after the NEWS ON THE MARCH reel, Joseph Cotten can clearly be heard saying..."Yeah, sure."