A common joke among the fanbase is of Afton's head shape being disproportionately large, often circulated with jokes and memes such as peanut and Jimmy Neutron. Later, a Reddit user examined Afton's head shape and found that it's size is actually closer to a real human's skull.
Scott's reasoning for keeping the game a secret for so long was because of a steam post from someone who was annoyed by the continuous teasers from previous games as revealed in Dawko's interview.
Most if not all the salvageable animatronics are redesigns. Afton being the most obvious, with a skinner built and bigger head.