I'm having a Mandela Effect

Nah, since you were only 4, it was probably all in your imagination. This song was never in the movie

I've never heard this song before or heard it in the movie. It's possible you might remember a clip/commercial or tv show that used this song with that section of the movie and it stuck in your head.

No one beats Christopher Reeves!

Yeah possibly Mandela Effect.

The song lyrics you're quoting are from Herbie Mann's "Superman," a disco hit specifically released to capitalize on the film's release but otherwise completely unrelated to the film.

Rather like Falco's "Rock Me Amadeus," very likely written to capitalize on "Amadeus," the hit film from the previous year.

Besides, it wouldn't fit with the John Williams score. Soundtracks back then (and today for the most part, "Guardians of the Galaxy" being a notable exception) tend to be internally consistent. If the soundtrack were to include pop/rock songs, the entire soundtrack would follow suit, e.g. "Flash Gordon" with its soundtrack by Queen or "Ladyhawke" with its Alan Parsons Project soundtrack.

While it's conceivable that there's some official version of the Superman film that includes Mann's song, there are also a number of YouTube videos that combine the two, so it's at least possible THAT's what you're remembering.

Or it really is the Mandela Effect -- I can't count how many movies from my youth look completely different from how I remember them for exactly that reason. My earlier brain perceived them differently and mis-wrote them onto my brain's hard drive.

Or ... again ... there really is some broadcast or VHS version out there that combines that song with that film.

Your nutty brain combined the song and the scene, and the two just do not jive together.

I don't think it quite qualifies as Mandela effect because that's not a real common false memory. At least I've never heard of anyone else remembering it that way! Mandela effect usually refers to things like people remembering Jaws girlfriends in Moonraker having braces. A lot of people remember it that way.

Sorry for being nitpicky. Other than that, it does sound like a Mandela effect style false memory.