Probably this is another pet of Avatar Aang, who was frozen in an iceberg for a hundred years. This cute puppy wasn't shown in the series, but he can be in our mind's plot due to our Dog in the Ice Sticker. You can be sure this dog is as good as it was one hundred years ago. Though it is not likely for a dog or any other living creature to be frozen in ice for 100 years and stay alive - in our imaginary world, everything can happen.