From YT:
A superstructure, kept upright by a constant flow of cats. I'm kidding, it's just a fountain of cats.
Looped animated gif http://imgur.com/uWQEI
Looped video of just a stream of cats http://youtu.be/Pad-a98MV78
Reddit thread http://www.reddit.com/r/Minecraft/comments/q8h0h/