Theory:the little girl on the sb ruin teaser is a robot version of Charlie because in the book series Henry was able to create robot versions of Charlie so if he was able to do it in that universe he’ll be able to do it in this one
My theory: William afton Created the nightmare animatronics. Reason 1: FnaF 4 Game over screen, Why would it be blood stains, If they aren't real? Reason 2: Burntraps arm, Looks like nightmare Freddy's arm, Doesn't it?
