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).
Purple Martin. Progne subis. The Purple Martin is considered to be America's most wanted bird. The interaction between man and martin dates all the way back to the Native Americans. To this day, the purple martin, with its bubbly personality and gurgling song, is cherished by many that host them.