Minecraft in Minecraft - Just a Matter of Time
Minecraft in Minecraft - it's one of those things people have been joking about since redstone first became a thing in the game. However, MrZeffoes has decided to go outside of humorous theory, and actually create the game, inside the game. With 8 different blocks, functional gravity (for player and sand), and an expandable 32x32 world, you can play Minecraft inside Minecraft all day!
Be sure to check out the for download links (snapshot 14w20b or higher required to run it)!
It's already happened, multiple times in several different formats.
I knew this was coming eventually
I don't think that's even possible, I mean there COULD be some way to make it 3d, but it would have to flip between the X axis, and the Z axis, it would be more of a pseudo 3d.