Of course slime has always existed but this YouTube slime movement is way bigger than anything that was on Nickelodeon. I don't think you realise the magnitude.
Purely anecdotal, but I was a kid during the Nickelodeon era. I bought 1 little plastic container of gak at that point. It was neat, but not novel enough to consider a big memory.
My daughter? Had me buy a book for her from some girl that she said is on YouTube who makes slime (the book is about slime), she wants glue and other items for the mixture almost constantly, and if she sees a container of slime at Target that looks cool, that's the toy she wants over anything else.
It'd be one thing if that was just her niche, but damn, her friends are all about it too. It is kind of insane.
I grew up in the Nickelodeon era. Pretty much every child star at the time, got slimed at some point. And Nickelodeon had their own amusement park with slime themed attractions. Every kid whose family had cable seemed to watch Nickelodeon. I came from a poor family without cable and I honestly thought that the Nick shows were a bit too corny and homegrown. So perhaps I noticed the culture more because I was a bit eyerolled by it. But it was a halcyon for sure..a staple of my generation.