Childlore is folklore passed directly between children, without the input of adults.
https://en.wikipedia.org/wiki/Childlore
Stuff I can think of off the top of my head are paper fortune tellers, summoning Bloody Mary/the candyman, the cool S, parody songs like “Jingle bells Batman Smells” and “Joy to the world, the teacher’s dead” etc.
This stuff has intrigued me since, well since I was a kid. I always wondered where they came from. I never saw adults doing that stuff, so I figured another kid had to have come up with it.
These video game ones now have me wondering if anyone else was told they could unlock extra characters in Super Smash Bros (N64) by clicking certain names in the credits.
The methods for unlocking these supposed secret characters were always ridiculously convoluted, so if it didn’t work you were probably doing it wrong. Like beating the game 10 times on level 9 difficulty with 1 stock with Pikachu would unlock Mewtwo, etc.
But like I said above, the stuff that was legit was often so weird and seemingly arbitrary that the fake stuff sounded more plausible. Talk to a specific NPC, fly to a specific area and surf up and down a specific coast, and you’ll encounter a glitched pokemon that will duplicate the sixth item in your inventory. Yeah it was all about memory registers or whatever, but I didn’t know about that stuff at the time.