Through a hack, the map system in Minecraft can play Nyan Cat videos while you build.
The new map feature included in Minecraft update 1.6 can do more than show where you are in the world. Through a hack, maps can also be used to display pixelated YouTube videos.
YouTube's "sk89q" first demonstrates the hack by playing a couple of music videos from Verve and DeadMau5. He then moves on to show the Aperture Science Turret trailer from Portal 2 and a Mirror's Edge video.
Both play right through the map even while sk89q moves around the world a little bit. He shows how deep the rabbit hole goes when he plays a video of himself playing Minecraft and using the hack to play a video of the Nyan Cat.
It's a neat hack, but sk89q admits that how it's currently performed is "unrealistic." However, he's looking into the possibility of a real YouTube player for Minecraft, should anyone want to use the game as an interface to get their Nyan Cat fix.