things you knew about but you didn't realise were hugely popular/viral until much later

A mirror of Joel's thread.

Basically channel your inner hipster.

What things did you remember fairly well but had no idea they were to become so popular and well remembered?

For me it was the OVER 9000! meme.

That one line in the show stuck out a bit oddly when I first saw it on Cartoon Network, (among many, it must be said) but I never anticipated that it was going to be so well remembered that it pretty much became the most definitive meme of its kind. I didn't know what a meme even was the first time I saw it, (did internet memes even exist in 1998?) so I was really surprised to find that people remembered it as well as I did.

I think there was only 1 other kid at school who briefly talked about that show, so I assumed that it wasn't all that popular. Not anywhere near as popular as Pokémon was when that rolled out; more than half the kids at the school had Pokémon cards and played the Gameboy games and we played link battles and stuff. So at that time DBZ was an obscure sideshow that was rarely talked about by comparison.
Roses are red
Violets are blue
Omae wa mou

Quote by Axelfox
Nightmare Before Christmas was one of my favorite movies as a kid and i didn't realize how popular it was until around the time i was in middle school.

or at least that's when hot topic started selling tons of related clothing.