I really enjoyed Korra, I thought it was a fun series. My favorite character was Bolin, he was so fun to watch. :D
I think my favorite nod was to the fans in the first episode:
Jinora: Gran Gran, I've been reading all about your old adventures. I've been dying to ask you, what happened to Zuko's mom?
Katara: Well Jinora, its an incredible tale...
Ikki: GRAN GRAN! you look old. How old are you? And why is it so cold in the South Pole? Can we make a campfire, and all huddle around it, and tell scary stories, and make snowmen? And then can you make the snowmen move with waterbending and chase us? Wouldn't that be fun? Huh! Wouldn't it?
Bryke must have been channeling their inner trollface.jpg. They must relish messing with us fans. :)

And the new Thundercats is great too, it's just too bad that it was canceled. Makes me sad, it had potential. :(

That scene was so funny XD I think my biggest surprise was hearing Dante Basco's voice again as General Iroh. I almost spit out the water I was drinking at that moment X3 and they're just so many more little nods that only true fans would catch, it just makes it awesome X3

And yea, I was definitely bummed about the Thundercats cancellation...I too thought they had a great thing going :/