Revealing mistake: After getting blasted by the big missile, as Superman goes to leave the rock face, the surface flexes, showing it's fake.
Revealing mistake: As Superman takes off from the junkyard, the background can be seen through him.
Continuity mistake: When Superman takes Clark's glasses, he folds one arm of the glasses in. A moment later, that arm is extended, and he folds both arms and crushes them.
Revealing mistake: After throwing Clark into the compacter, Evil Superman flies to the control booth. As he walks through the door, the background can be seen through him.
Continuity mistake: When the toy penguin waddles into the smudge pot, its right wing and head catch fire. When Clark sees it, only a small amount of flame is on top of the head.
Revealing mistake: As Evil Superman quips to Clark about wanting to fly, as he struggles Clark's left shoulder goes a little transparent, showing his image was superimposed over the stunt actor.
Revealing mistake: After Clark defeats Evil Superman, he flies to the Statue of Liberty. The whole landscape is a still image with the ripples and the boats completely static.
Continuity mistake: In the junkyard, when Clark comes out of the container, the hole he produces changes shape depending on the angle.
Continuity mistake: Evil Superman is chasing Clark on a conveyor belt and starts to shout and move swiftly as if he was flying. A frame later, from another angle, he is calmed, walking and repeating all previous movements.
Continuity mistake: When good Clark is on the trash compactor about to be covered in metal parts, he lays on a blue car hood. Depending on the angle the hood is barely rusty or very rusty.
Continuity mistake: When Gus is biting Ross, his hand rests on Gus's cheek, a frame later it rests on his head.
Continuity mistake: When Ross is staying late at work, two women are taking their tennis shoes off. When the angle changes, the woman on the left is walking towards her locker and grabbing her tennis shoes again.
Continuity mistake: Noticeable hand-double during the close-up of Gus unscrewing the fuse: Very dark skin and long fingernails as opposed to Gus's short nails and light-brown coloured hands.
Continuity mistake: Before Vera is transformed into a robot, her face is covered in thin wires. A frame later they're gone.
Continuity mistake: When Gus stays to work extra hours at the office, there are two girls in the background. A paper on the right appears / disappears between shots.
Continuity mistake: Before the phone booths fall, the street swaps from being in shades to really sunny between one frame and another.
Continuity mistake: At the bowling alley, when the kids are about to choose Ricky, the kid on the left keeps changing between a tall kid to a small one with a hat on, back and forth.
Continuity mistake: Gus takes off the fuse off of the computer crying "I did it", then bends his arm towards his chest. A frame later, the arm is extended outside towards Ross.
Continuity mistake: After Gus places the supercomputer blueprints on Mr. Webster's table, they change positions between shots.
Revealing mistake: When the firemen's truck runs out of water there's a close-up of the level meter and it reads "Pierreville fire trucks Ltd. Camions a incendie" revealing the scene was shot in Canada.
Answer: The only reason that Gus was working with Ross, Vera and Lorelei was because he stole money from the company he worked at. To avoid going to prison, Gus was forced to do anything that they wanted. After realizing that his computer was designed to do anything it was ordered to, including killing Superman, Gus removed a small screw which shut down the power momentarily but, after the computer brought itself back online, Gus attempted to destroy it with an axe to save Superman. Superman saw this and realised he was wrong about Gus and after the computer was destroyed decided to help Gus find a job.
That makes sense, thank you! Been bugging me for years.
Jen Hen
You're welcome.