This error caused debate over whether William or Michael was killed inside Springtrap, until Scott's response to one of MatPat's Five Nights at Freddy's theory videos, as well as the credits of Freddy Fazbear's Pizzeria Simulator, confirmed William as the spirit possessing Springtrap.

What animatronic does William Afton possess?

Five Nights at Freddy's 2

They go on to possess the Freddy Fazbear, Chica, Bonnie, Foxy, and Golden Freddy suits. The Puppet would give them life in the animatronic suits to save their souls. It's unconfirmed whether William or the Puppet stuffed the children into suits.

Who is Springtrap possessed by?

Springtrap, previously known as Spring Bonnie and William Afton, is the main antagonist of Five Nights at Freddy's 3 and the withered form of Spring Bonnie. He is possessed by William Afton. He appears in Five Nights at Freddy's VR: Help Wanted and Five Nights at Freddy's AR: Special Delivery.