These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
YMMV: Superman III
Alternate Character Interpretation: It is not clear exactly how much Ross buys into Loreli's airhead act. Most of the time he seems entirely fooled but in one scene she winks at him while Vera isn't looking, suggesting it might be a game the two are playing.
Big Lipped Alligator Moment: The scene where the two traffic sign 'walk' and 'don't walk' figures fight each other. It's weird, bizarre, and nonsensical even in this context, and isn't mentioned again.
The "junkyard fight" between Superman and Clark Kent verges on this, even though it ends with Superman becoming good again and is thus important to the plot. In any case, it's commonly regarded as the best scene of the movie.
The slapstick opening sequence doesn't belong with the rest of the movie, as if the reels were switched with one from a Police Academy movie.
Ensemble Darkhorse: It's probably inevitable that Lana didn't return for the fourth movie, because too much more time spent with her and the audience would have been seriously questioning what Superman ever saw in Lois.
"You can't run two programs at once". Tech Marches On; your computer is doing it right now.
A meta example is Annette O'Toole playing Lana Lang here and later playing Martha Kent in Smallville.
Hollywood Ugly: Vera. They make her sound like Quasimodo, but she's a handsome woman.
Nightmare Fuel: It looks silly years after, but a certain scene in the climax was certainly this. People who haven't seen the movie may even be familiar with it. If you don't want to click the link: the computer the villains built turns against them, and as they flee, it catches Vera. It pulls her inside its workings and turns her into a robot. This scene likely scared more children than any other scene in the entire series, not helped by the fact that it's easy to miss that she returns to normal once the computer is destroyed.
Sequelitis: Usually considered the worst Superman film by fans. Most will concede that Superman IV: The Quest for Peace is worse in technical quality, but will gladly accept its whole-hearted (if veryAnvilicious) attempt at a message over this film's broad comedy and Richard Pryor's spotlight stealing antics and, being as loaded with unintentional hilarity as it is, it's easy to argue that Quest for Peace is the funnier movie, too.