Pokemon apparently. I guess there’s never been a mental Floss episode about it. (Full disclaimer - not having kids, I definitely know even less about it. And what Green knows about it doesn’t really make me regret it... ;)

https://www.youtube.com/watch?v=lkad723GsvA

EDIT: Video doesn’t embed. Also - the site looks stupid, now. Why is the side bar taking up a quarter of the screen?