Herobrine
Watch in high resolution, while I was recording this it was a lot brighter than it ended up being. The reason I paused (in case you can't see it) was because I saw Herobrine there and rightfully sharted myself, although it's rather hard to see with this video being so dark on Youtube.
The original purpose of this video was to show my friend (who doesn't play Minecraft) what I mean by "Minecraft can be beautiful". I wanted to show an example of how the random terrain generator can make very cool things. I went exploring to that purpose and found the semi-roofed cave in the video, and I immediately put on Fraps. When I went into it, though, I recieved a bit of a shock.