The main object that caused such a supernatural phenomenon is the remnant, a metallic substance that can confine souls into inanimate objects, causing them to become alive. The remnant was discovered initially by the Puppet, who used it to give life to Freddy, Bonnie, Chica, and Foxy with the first couple victims of William. The remnant was later discovered by William as well, which he incorporated into many of his Funtime animatronics, causing them to become alive. Another interesting theory is that William also integrated the remnant into the Scooper, which explains why Micheal Afton's soul was still bound to his body after getting killed by the Scooper.