Animatronics

The animatronics are the main antagonists of the Five Nights at Freddy's game series. In FNaF Universes, they are the main characters (or rather a nation).

Description
Animatronics (or mascots) represent the usual animals, people and dolls. By day, they entertain visitors, and at night roam Freddy Fazbear's Pizza in the "free action" because animatronics don't have long to remain disconnected, otherwise their servos are locked (according to Phone Guy during a call on the first night). In the FNaF2 Withered Chica's beak always stays opened because its servos were permanently locked in the opened position. If a human appears in the pizzeria after hours, the animatronics will see him as an endoskeleton without a suit and try to put him in the Freddy suit, in the workshop, which will kill him.

Theory

 * Interestingly, Puppet is not an animatronic, according to Phone Guy in FNAF2.
 * In the workshop, in FNAF1, we see a bare endoskeleton, the strange thing is that when Bonnie comes back, he doesn't put him in the suit, although they had a program of putting the suits on the endoskeletons.