Hello fellow A:TLA/Korra fans! I'm sure most of you has heard about this rumor that has been around since late January. Which is that Studio Pierrot is doing the animation for book two, rather than Studio Mir. This was first confirmed by LeSean Thomas who did the storyboards for book one. If you would like to check out his tweet, Here you go! Now, he pretty much confirms it. He is considered a reliable source.
Then we get an interview with the one and only, Yoo Jae-Myung! In the last 5 minutes or so, he explains what is going on! He informs the interviewer that Studio Mir was originally going to work on book 2, but they were also offered to animate a season of "The Boondocks." So they were conflicted about whether to take on both series, or to just do one. Then, they decide to only animate The Boondocks because they were very exhausted from animating book one because it was very challenging. So, Bryke started working with a Japanese Animation Studio called "Studio Pierrot." According to Yoo jae-Myung he speculated that there were many problems with Studio Pierrot. So Bryke asked them to be in charge of book two as well. Which means, that both Pierrot AND Mir worked on book two. They realized that if book two is met with bad reviews, that both Mir, and Korean animators reputation would be tarnished. He also stated that Mir will stay till' the end now matter how hard it gets, which means that they will be animating books three, and four as well. :D
I would lean towards Studio Mir doing all of Book 2 as I think the interview made it very clear that Mir did not want any other studio giving them a bad name, by not living up to their quality. It would also explain why Book 2 has taken the longest of any Avatar season to come out. The animation looks different slightly in the final clip that we saw, other than that everything else looks normal. The Spirits in my opinion are purposely animated in a different style to show they are not from the physical world, and are different to the spirits we have seen before. The other off scenes I would put down to a bit of us all over analyzing a few seconds of footage, footage that is comprised of action shots. Do the same to more or less any scene in A:TLA, or Korra and you will see some odd parts of the animation. If Pierrot had any involvement in Book 2, which I think will be very minor, perhaps just a few scenes or maybe an episode, Mir may have possibly edited their work. It is important to note how confused most people working on the show seem to be about it, we definitely do not have the full story.
This was also my first blog, so I hope I did well. Thanks for reading!
Edit: Also, there is also a theory that Studio Pierrot IS doing the animation, but Mir is overseeing it, which means they're editing it, because apparently Pierrot's not doing so hot with the animation.
Edit 2: The theory above this edit has been confirmed! The animation in Book 2 is outstanding!