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 People Eaters (sometimes Purple Gang) were the defensive line of the Minnesota Vikings from the late 1960s to the late 1970s. The term is a reference to a popular song from 1958, the efficiency of the defense, and the color of their uniforms. The motto of the Purple People Eaters was Meet at the quarterback.. One of the original members of the defensive line, Gary Larsen, was replaced in the mid-1970s by Doug Sutherland.