Although seeming very cryptic at first, William's character traits and nature can be seen via silent actions within retro-graphics and by reading between the lines throughout the games.

William Afton is the textbook definition of evil. He is the sadistic and depraved serial killer who sparked the downfall of his own company, Fazbear Entertainment. He murdered almost a dozen children in cold blood, and started the tragic chain of events that leads various players throughout the series.