Revealing mistake: In closeups, you can see Lex Luthor has a bald cap on.
Suggested correction: Much too vague. What scenes are you referring to. And how can you tell, other than knowing that Gene Hackman isn't really bald?
At the end of the movie, in the prison yard, when Lex took off the wig he was wearing, showing that he was bald, the wrinkles were unnatural, suggesting a bald cap.
Revealing mistake: When Zod is thrown by Superman and passes by Luthor, the stand in is a guy with fluffy hair who looks nothing like Lex.
Revealing mistake: When there are multiple Superman's in his home, Lois Lane runs to one of the fakes. It seems as if she is the fake because her image becomes slightly transparent as she runs through him.
Revealing mistake: Wires holding Superman are seen when he lands on the island to pick up fruit.
Revealing mistake: After Superman saves the kid at Niagara Falls, he lands on a lawn nearby. Then wires holding him are visible.
Revealing mistake: When Zod takes the rifle out of the cop's hand the strings moving the rifle are seen, each by the side of the cop's cowboy hat when the rifle turns red.
Revealing mistake: The 3 villains break through the Daily Planet window and fly around the city. Before Zod stops by a beam, Non becomes transparent.
Revealing mistake: After the Marlboro truck scene, Superman throws Zod and he goes through an office window. The harness to make him fly is visible on his back.
Revealing mistake: When Ursa blows the helicopter away, the string holding it is visible.
Revealing mistake: When Non falls on Superman and breaks the concrete, the hole opens before Non falls on him.
Revealing mistake: When Non goes through the pavement, the hole reveals it's a foam made floor.
Revealing mistake: In the ice cave, when Superman makes himself invisible, watch Zod's head jumping slightly to the back, revealing where the scene was edited to achieve the effect.
Revealing mistake: In the ice cave, Superman throws a plastic S at Non. The wires moving it are visible.
Revealing mistake: During the big fight in Metropolis, the close-up of the pram shows its empty or with blatant bundled pieces of fabric to simulate some sort of baby.
Revealing mistake: When the Empire State antenna falls down the wires holding it are visible.
Revealing mistake: Near the end when Zod and his crew are blowing everybody away, there is a shot of two cars going into a department store and one flying right to left. There are also two "people" running away in this shot. They're dummies. One of the cars hits the person and he wobbles. Incredibly obvious. These aren't mannequins from the store either; they're on a track and follow a path from right to left.
Revealing mistake: When Zod picks up the guy in East Houston, you can see right through the guy. He's transparent.
Revealing mistake: When Superman is saying, "No, don't do it! The people!" you can see Christopher Reeve is trying his hardest not to laugh.
Revealing mistake: All of the movements of both people and objects on the moon are played in slower speed to simulate the Moon's gravity, except for the last scene where Zod grabs the oxygen tube and it falls on the ground at normal speed.
Revealing mistake: When Non flies through the White House ceiling, right before he lands on his feet, the shot cuts to Zod landing safely and one can see that the previous stuntman missed the landing and fell on his back, his legs now pointing upwards. According to the shooting script, the fall was not scripted and not plot-wise.
