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).
It was believed that Mike was the African-American fighter who was punched by the blond fighter in the Street Fighter II intro but the Street Fighter V website later revealed that the African-American character in the intro is a different character named Max while the blonde fighter is named Scott.