So I've had the Legend of Korra finale stuck in my head for the past few days and today, I was stuck by one thought: boy, the universe of Avatar is weirdly similar to the universe of Brandon Sanderson's Mistborn. They act, I think, as parallels of each other in a way.
1. First up, both have a well defined system of magic. In the Avatar universe, magic ("bending") is based on benders manipulating one of the four elements, with the Avatar able to bend all four of them. In the Mistborn universe, magic ("allomancy") is based on Mistings ingesting and "burning" one of sixteen metals which allows various physical/mental abilities (steel lets you push, iron lets you pull, tin enhances senses, pewter enhances strength, etc.) with the extremely rare Mistborn able to use all sixteen metals. (Okay, I'm oversimplifying, because Sanderson's magic system is extremely complex and even has two other magic systems to complement it, Hemalurgy and Feruchemy, but still.)
2. Both have the Chosen One. In the Avatar universe, obviously, the Avatar is the Chosen One, meant to maintain balance and act as a bridge to the Spirit World. In the Mistborn universe, the Chosen One is called the Hero of Ages and...well, it's kind of complicated, because it involves the manipulation of prophecy and a lot of subversion. But in the end (SPOILERS), the Hero of Ages does bring balance to the world.
3. Both have a spirit of light/life fighting against a spirit of darkness/death. In the Avatar universe, it's Raava fighting against Vaatu. In the Mistborn universe, it's Preservation fighting against Ruin.
4. Okay, both have kick-ass female main characters.
5. Neither world stays static. In the Avatar universe, after seventy years, they have cars and radio and movies. In Mistborn, after three hundred years, they have cars and trains and holy crap so many guns. (The difference in time is that in the Avatar: The Last Airbender, they were already using tanks and airships; in the original Mistborn trilogy, they only had horses, with every technological innovation suppressed by the Lord Ruler. It probably took them much longer to get up to Avatar's level of technology, although they don't have guns in the Legend of Korra.)
Okay, a lot of these are superficial similarities, much like the similarities between the X-Men and the Doom Patrol. The Avatar universe is based on Asia and that's where most of it's imagery comes from; the Mistborn universe seems very much based on Europe and America (especially The Allow of Law, which is basically a Western). And the stories both branch off in completely different directions.
In any case, this was just a neat thought I had.