What Happened to this Minecraft World?

I'm a little sick right now, but I wanted to show off this cool... Bug? Glitch?? That I found, so here's this quick video. It actually took quite a few tries to get it to work! And even after that, I couldn't get the type of glitched world that I originally had on my USB drive all those years ago.
Maybe I will never find it again...
Feel free to try it for yourself!
I hope you enjoy :)

Видео What Happened to this Minecraft World? канала Squiddo