A voicemail message left by Mike’s predecessor explains that the animatronic animal characters used at the restaurant—including the titular Freddy Fazbear, Bonnie the Bunny, Chica the Chicken, and Foxy the Pirate Fox—are able to roam freely around it at night, because if they were left off for too long, their servo motors would lock up. He also adds that the characters were no longer allowed to roam freely during the day following an incident referred to as the “Bite of ’87“, which apparently involved the loss of someone’s frontal lobe. The employee warns the player that if one of the robots encounters a human, they will automatically assume that it is a robot that is not in costume yet, and “forcefully stuff them” into a spare mechanical Freddy Fazbear costume, killing them in the process.

Learn more about the characters:

Freddy Fazbear
Bonnie
Chica
Foxy
Golden Freddy
Mike Schmidt
Phone Guy

Five Nights at Freddy's characters