The First Thing I thought about....

So, the animatronics that got carried on from the original FazBear Entertainment center were, Spring Trap, Mangle, and Marionette! The Reason Foxy didn’t come to sister location is because Mangle got fixed and turned into Funtime Foxy. Now there is one human that made this huge mess that human is William Afton. He made this mess because ever since his family died he started to kill other kids so they would know what the pain feels like. So,Afton had a lot of trust in some old animatronics to lure kids so he could kill them. I suspect he kept some of the old animatronics from Freddy Fazbear Pizzeria Because the bite of “83” and “87” Happened there. So he kept the animatronics to remind him of what he did. (I also added Spring Trap because Afton died and became Springtrap so that's why I also added Springtrap.)