Continuity mistake: In the Olympics ceremony, the file footage shows very few people by the final steps to the cauldron. When the shot changes to the modern footage, a lot of people have suddenly appeared there, plus they change bewteen shots.
Continuity mistake: When Ross is reading a newspaper in his office, the black paper clips move around between shots.
Continuity mistake: Before Gus gets on the skis his shoes are grey with thick black stripes. When he lands he has plain brown shoes.
Continuity mistake: When Evil Superman arrives at the oil tanker, the tower on the deck disappears in the close-up where he opens a hole in the steel.
Continuity mistake: When Jimmy takes the picture of the Stokis, he lifts his finger from the camera and raises his head. In the following angle he repeats every movement.
Continuity mistake: The toy penguin that catches fire is already burned and damaged, when it's supposed to come brand new from the seller's stall.
Continuity mistake: When the bucket of yellow paint falls on the old man, he turns around and starts to walk backwards. In the next shot, he is facing forward.
Continuity mistake: The lid that falls on Clark has a bumpy side. One of the shots shows the lid falling with the bump pointing at Clark's head. For the rest of the shots the bumpy part is on the left side.
Continuity mistake: When the bus that Clark and Jimmy are on pulls up to the traffic jam, you can see the smoke from the fire is wafting all over the place. When the angle changes when the two climb off the bus, however, the smoke is limited to the distant view.
Continuity mistake: When Superman arrives at Pisa for the second time, the sky changes from violet to blue.
Continuity mistake: In the bar, while bad Superman is destroying the bottles, the way they are placed and the ones that are broken or undamaged keeps changing between shots.
Continuity mistake: Bad Superman punches Clark and he lands by a car door. In the next shot the door has magically moved on top of him, which makes Clark take it off of him.
Continuity mistake: When Clark is choking bad Superman, his right hand cleans itself after Superman disappears.
Continuity mistake: When Superman lands in Ross's attic, a chair moves to the left between one shot and another.
Continuity mistake: While bad Superman is in the bar, the whiskey bottle's label faces the window. From the window's point of view there's no label seen.
Continuity mistake: On the Grand Canyon, when Gus is about to get on the donkey, the first shot shows him several meters ahead of Vera. The next aerial angle shows him very close and parallel to her.
Continuity mistake: During the credits, a red and white pole with a light on top appears to the right of the crashed green car.
Continuity mistake: After Superman is swallowed by the super computer, red acid spills on the computer. Right before the acid breaks the floor, the computer is shown again, completely clean.
Continuity mistake: In the wheat field, after Superman brings Ricky, the upper sleeve from the pullover tied around Lana's neck changes size after Superman leaves.
Continuity mistake: After Superman fixes the oil tanker and touching the oil soaked steel, he waves goodbye to the sailors and his hands are clean.
Answer: There were rumors that Hackman was angry with the Salkind Brothers (the producers) for firing director Richard Donner, though Hackman later disputed saying that. His explanation, though he may have been downplaying the real reason, was that he had a number of other movie projects at the time, and he also did not wish to continually play the same villain in an ongoing movie series.
raywest ★