Factual error: When Superman addresses the UN, the delegate presumably representing the United Kingdom appears behind an "England" sign - "England" is not an international entity represented at the UN, while the United Kingdom of Great Britain and Northern Ireland is.

Visible crew/equipment: When NuclearMan enters the building after being told he would be taken to Lacy, he flys upward through different floors. As he's doing this you can see support wires attached.

Continuity: When the volcano erupts, there's suddenly a lot more snow on the crater.

Revealing: Nuclear Man is shown blowing up the Great wall twice, but it's the same shot reversed.

Continuity: When in the subway, Superman is standing by a 6 foot poster of the Statue of Liberty. When the shot changes to a flying Superman, he is a third of his size and the poster is huge.

Continuity: In a split second, all of the snow on the mountain cut by Superman disappears.

Continuity: When the statue of Liberty is about to crash on the street, a close shot is seen of jammed cars and hysterical people. When the shot changes to Superman flying to the rescue, the jam, the cops and the people have disappeared, and all is nice and quiet in Metropolis.

Revealing: The rock that hits the prop-astronaut blows his head off. Seconds later the head is back in place.

Factual error: If the Russian cosmonauts need special suits to survive out to space, so does Lacey when she is taken by Nuclear Man.

Continuity: The cab's hood, crumpled by Nuclear Man's power beam, magically smoothes itself a frame later.

Continuity: Nuclear Man lands on a street surrounded by skyscrapers. In the following shots where he destroys everything, the right side of the street is the same, but the left side is totally different: small houses, sunnier, signs on the walls.

Continuity: Two firemen are seen away from their truck, but when the angle changes six firemen have appeared seemingly from nowhere.

Continuity: The bundle that Superman makes to destroy the weapons changes to a tenth of its size in about a second.

Continuity: Nuclear Man dents the floor with his footsteps, but in a wider angle the floor is intact.

Continuity: When Superman and Nuclear Man fight on the balcony the high powered binoculars disappear.

Visible crew/equipment: In the quarry, when the cops' car flies up the air you can see the ramp used to lift it on the lower left side of the screen.

Revealing: When Clark Kent enters the subway, the set is the same as the rampage later in the film; only that the second time we see this set, the subway entrance has vanished.

Continuity: During the volcano eruption the animal on the right (goat or sheep, I don't know) keeps changing from brown colour to white.

Continuity: When Lacy is about to enter the elevator, a light brown rug has appeared on the floor behind, which disappears in the next wide shots.

Deliberate "mistake": The same front shot of Superman flying is used over and over and over again.