"Avatar: The Last Airbender" is my kids' all-time favorite cartoon, and it's actually one of mine as well. A solidly-defined 'novel for television' (To use the Straczynskian argot) with a definite beginning, middle, and end, the show managed to engage kids and adults alike. The animation was beautiful, as well.
(The less said about that M. Night Shyamalan atrocity the better. Seriously, why do people keep giving this guy money? I'll grant that he's made one very good movie, but he's made ten OTHER movies, all of which were very bad indeed. And he's trying to clamber his way on to the Harry Potter and Indiana Jones franchises, which is of course going to destroy either of them if he gets the gig, but that's a rant for another day)
"Airbender" was so popular, and the fictional world it plays in was so well developed, that it seemed almost foreordained that a sequel or spinoff would happen. And it has:
The thing is, this actually sounds pretty good. It's set seventy years after the first series ended, everyone we know is dead so the story won't intrude on their well-deserved happily ever after, and we also won't have to worry about their voices changing as happened to Chowder. We get to explore how the world our heroes created developed, it all seems rather cool, and of course the producers have more than earned my faith based on their past work.
But if that weren't enough, "Korra" is conceived of as a very solidly defined miniseries of just 12 episodes. Not a long, lumbering sequel that overpowers the original as TNG did Trek; not a "More of the same" sequel like Stargate: Atlantis. This is not an epic, this is a backwater, an eddy, a neat little side story that does things the original couldn't do, and doesn't try to recapture lighting in a bottle. Instead it goes after an entirely different kind of lightning.
Or so the concept goes. It's not at all sf, but I'm very much looking forward to it.