Ok. I have a theory. I think Bonnie was pregnant and Springtrap is the child. In FNAF2, we have withered Bonnie and her (sorry guys I believe Bonnie is a boy but Bonnie needs to be a girl for this to work) stomach looks a little swollen. Ok so there's a saying in England and its When a woman turns pregnant she loses her face. And Bonnie has lost her face. Then in FNAF1 Bonnie's stomach looks more swollen. Then in FNAF3 we see that Bonnie is flashing her eye on and off. Maybe she's looking for her child?
Please comment what you think.