The permaswap AU:

 When Sahara and Concorp's redstone work manages to break part of the code in the game, no one seems to realize it. Everyone in the server goes to bed and swap bodies with each other. When Tango, Void, and X try to fix the mess, they realize that they may not be able to swap everyone back. 

 The three hermits try something based on some old blueprints, but it leads to how the other servers get swapped around as well. Everyone also finds that they can't log out due to how their minds don't match the bodies' code. Everyone now has to adjust to their new bodies, powers, etc.

 List of swaps will be added later...