This Matt Cutts YouTube video is pretty neat.
Matt Cutts tweeted a link to one of his many videos... except this one is upside down.
I actually haven't quite figured out why this exists. It's not on the YouTube main page or other videos, so I don't THINK it's an April Fool's joke.
Boy, I wish I was a higher up at Google and I could just prank the Internet on a whim.