In some ancient civilizations the Wolf was a symbol of the underworld. In Egypt, the guardian of the dead was Anubis who was a wolf-headed god. The jackal portrayed as black was the symbol of both death and regeneration.
William is also the one who hid inside the suits and kidnapped and killed children, leading to the assumption that William Afton is The Purple Guy of FNaF 2 and 3 (he is killed at the end of the book when Charlie sets off the spring locks in his suit).
Now for the purple man I did talk about the purple man before but I never really did say who it could be. Okay I believe that it could be the phone guy or the security guard that you get on night 7 or 8 in Fnaf 2. The reason it could the phone guy is that he wants to make sure that no one finds out so he takes the security guard job in order to make sure that no one discovers that the kids bodies are in there.