Continuity mistake: In the gym, the way Ross places the white towel around his neck changes between shots. His hands are covered by the towel or on top of it, depending on the shot.
Continuity mistake: When Superman is landing Jimmy, a fireman in the back takes his oxygen bottle off twice.
Continuity mistake: When phone booths fall, they don't knock down a blue bucket; but a frame later, in a close up, it's seen down on the floor.
Continuity mistake: When Clark is trapped in the crunching machine, a blue piece of metal is left out. Two shots later it has disappeared.
Continuity mistake: When the telephone booths fall, the dog runs away. A second later it's seen back where he was running away again.
Continuity mistake: When Gus is trying to access the main computer, his reflection shows him bending down. In the next shot he is repeating the movement.
Continuity mistake: When bad Superman knocks out Clark with a kick on the face, his position on the floor changes between shots.
Continuity mistake: When Superman saves Ricky at the wheat field, the rock by his head disappears.
Continuity mistake: While the blind man is walking his dog, a man in blue jean walks by the left of a tree. There is a brusque cut and the man in jeans is now walking on the right side of the tree.
Continuity mistake: When bad and good Supermen is going up on the junkyard belt, one shot shows Clark very close to a car, in the next one he has gone down and the car is farther away.
Continuity mistake: When bad Superman is flicking the peanuts, the man by his left stands up and hides at the end of the bar. In the next shot he is seen close to Superman reflected on the glass.
Continuity mistake: The lady by the bingo trolley leans her head to the right and asks "Can we have the next number?" When the angle changes her head is now leaning the other side.
Continuity mistake: While in the bus to Smallville, Clark sees the accident on the heliport and there are no cars on the side of the road. From a shot outside it's full of them.
Continuity mistake: While Mr. White is trying to open the bingo ball, from the side shots the lady is watching the ball. From the front shots she is watching him. This keeps taking place every time angle angles.
Continuity mistake: The fireman on the right points at the lake and lowers his arm. In the next shot it's up again.
Continuity mistake: After Clark Kent smashes cake on a man's face, the amount of cake increases in the close-up, especially on his neck.
Continuity mistake: When a man tries to pick up the toy penguins, a close shot shows them walking, but on the wide shot they are standing still.
Continuity mistake: In the beginning, when Gus is waiting on the queue of the employment office, the amount of papers by his feet changes between the close shot and the wide one following.
Continuity mistake: In the employment office, the crushed Coke can jammed between the iron bars changes position between shots.
Continuity mistake: The location of the staircase leading up to the supercomputer's control console changes. When they first enter the computer, it is at the back of the computer behind a lot of electrical machinery and circuits. When Ross comes down to try and get the screw out of Gus's mouth, the staircase has moved right next to the entrance of the computer (where Vera gets turned into a robot later on).
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 ★