Springtrap

Springtrap is the main antagonist in Five Nights at Freddy's 3, and returns in the Five Nights at Freddy's: Sister Location Custom Night, as well as Pizzeria Simulator and Ultimate Custom Night. He is seen in the 10/20 mode Cutscene and in Circus Baby's second teaser. He is a heavily tattered version of the Springbonnie suit in which William is trapped inside.

History
Springtrap is a withered, decayed spring suit, in which william afton is trapped.

Spring Bonnie was an animatronic functioning with "spring-locks", created alongside Fredbear by Henry, and one of the first animatronics created in the Fazbear and Fredbear collective franchise.

Spring Bonnie made his first debut in "Fredbear's Family Diner", the original location which lead to the creation of Freddy Fazbear's Pizza.

He also made an appearance in the Five Nights at Freddy's 4 minigame restaurant, known as "Fredbear and Friends".

He was eventually replaced with "Bonnie", a dark blue counterpart with a slight redesign. Spring Bonnie and Fredbear were decommissioned from an incident called "The Bite of '83", shown in the FNaF 4 minigames.

William Afton stole the suit on several occasions and used it as a disguise to lure children into the back of the restaurants to murder them.

William met his death in a Spring bonnie suit, after an attempt to hide in the suit from the dead souls of the murdered children. When Afton hid inside of the suit he began to laugh and taunt at the souls, which resulted in a springlock failure from movement and moisture from his breathing. His soul possessed the suit, his body decayed inside the suit for many years until his appearance in Five Nights at Freddy's 3 as "Springtrap" and eventually in Freddy Fazbear's Pizzeria Simulator as well.

Silver Eyes timeline
In the SEt, William Afton is killed by Charlie (Henry's daughter in this timeline) inside the springbonnie suit. William later reawakens and creates the Twisted Animatronics (Silver Eyes version of the Nightmares), who he has help him in kidnapping and murdering highschoolers who attend Charlie's highschool.

Trivia

 * When Springtrap moves forward his right ear appears to be erratic.
 * In his original character description, William Afton was also known as Scraptrap, a fanmade name given from the community.