The Player is Henry
Another possible identity for the player character is Henry Afton. If you look a little closer at the theory that the player is actually William, there are a few details that don’t seem to fit. For instance, if we really were William, Circus Baby would’ve likely recognized him from day one. Instead of us being William, perhaps it’s more likely that Henry was the one who came to Sister Location out of the guilt he felt over Afton’s daughter’s death. We know from FNAF World that Henry was the one who built Circus Baby, so it’s possible that he felt responsible for creating the animatronic that took the girl’s life.
There’s also a theory that Henry is actually William’s brother (after all, we never get to hear Mr Afton get referred to by his first name), and this adds to the guilt that he felt over the girl’s death.
