How does the Phantom Zone get to our galaxy? Clark is sent there on a rocketship, but the last time we see the phantom zone it is floating away from krypton at its own pace. Chalk it up to a HUGE coincidence?

When the evil trio are on the moon they think Earth is called Houston. When they arrive on Earth they coincidentally land in Houston or do they follow radio signals which emanated from Mission Control?

When Lois jumps in the river...he melts a branch with his heat vision but he doesn't remove his glasses the heat vision should have melted the lenses on his glasses.
According to Superman No. 130/1 [July 1959, "The Curse of Kryptonite"], Superman, while he was still a youngster in Smallville, used the "plexiglass shield" from the wreckage of the rocket ship that had brought him to Earth to fashion the eyeglass lenses he now wears in his role as Clark Kent. "These super-plastic lenses don't melt when I project my X-ray [referring to both the X-ray vision we think of today and heat vision]
vision through them!" thought young Clark Kent at the time. "Ordinary Earth glasses would! As for the rims, my X-rays never touch them!" and also, in the next paragraph, (possibly just a tiny bit off the point, though)
Superman No. 146/1 [July 1961, "The Story of Superman's Life"] confirms this account, adding that that smashing of the rocket's "super-plexiglass" shield when the rocket crash-landed produced four "fairly round pieces" ideal for use as eye glass lenses. "What luck!" thought the young Clark Kent as he examined what remained of the wreckage.
"When the super-plexiglass smashed, four farly round pieces were formed! I can make plastic frames to conceal the uneven ridges! I'll have glasses...both for my boyhood and manhood...that are impervious to my X-ray vision!"
This also shows that if Clark does pull down his glasses (without, of course, losing or destroying the ones he had), such as in Lois and Clark, that IS a blooper.

During the Houston fight, Zod lifts up a man using a beam which emanates from his finger; The man's son who begs Zod to, "Please put my daddy down," speaks with an English accent, something not very common in Texas.

Superman said he found the green crystal when his father died, but then Martha's hair must have turned white overnight.

How did Lois and Clark (without his powers) get from the Fortress of Solitude to the car.

How long did it take for Clark to get back to the Fortress without any help ?

Noticed that when the three from the Phantom Zone invade the Daily Planet Lois's hair goes from frizzy to smooth every other scene. At first Lois has a lot of make-up on but miraculously disappears a few minutes later. - Alternating between Donner and Lester shots.

When Superman crushes General Zod's hand and picks him up. Take a look at his armpit, there is a noticeable sweat mark.

At the end of SUPERMAN II extended version, Lex is trying to make a deal with Superman. When making up boxing names for Superman he mentions Smallville. How would Luthor know about Supe's hometown without knowing about his secret ID? Or did Superman have to erase his mind with a kiss as well?

The ending scene where Superman is flying towards the White House to replace the American flag. In the far shot, you can see that the background is absolutely fake because the spouting water fountains are frozen in mid-air...Superman is flying against a STILL photo of the White House.