Found this in an old WiP folder. I think it was a plot bunny for... something. Probably a thread on the Spacebattles forum. To sum it up, it was a stab at creating a "mirror universe" without the usual morality swaps of a good Fire Nation, evil Water Tribe, and goateed Spock. Everything in the Avatar universe gets inverted. I dusted it off, gave it a once-over, and finished it to post here.
( AtLA: Opposite World )