Springtrap AKA Spring Bonnie is an animatronic and is the main antagonist of Five Nights at Freddy's 3. He is also the only animatronic who can kill the security guard unlike the Phantom animatronics.
Springtrap is a brownish-golden color resembling Golden Freddy. Its "fur" is rotted, and it has copious amounts of external damage. It bears human-looking eyes, and a deranged smile, likely due to decades of neglect and general wear-and-tear. It resembles both Bonnie and Golden Freddy in many aspects. This mysterious animatronic also has a very spastic, convoluted way of moving, and a loud, electric-sounding scream, like the other animatronics.
Springtrap was a prototype animatronic suit, designed both endoskeletons and humans. However, the suit's spring-locks were loose, and malfunctioned easily, causing the suit to contract and tighten if ever they did, crushing any human inside, thus deemed extremely dangerous. For this reason, Springtrap Bonnie was abandoned in place of the current animatronic suits and left to rust away.