A Nest for What Kind of Creature?

Addie's hair is pretty wild, especially when she wakes up. However, on this evening, she had her bath, hair brushed, teeth brushed, and waiting for her milk...she was on her back waiting for me and when I picked her up, her hair was a disaster! I am not sure what kind of animal is living in her hair on the back of her head, but OMGoodness! She has a mess!