Bonnie is one of four main antagonists in Five Nights at Freddy's. Like Freddy Fazbear and Chica, Bonnie is a children's entertainer during the day, housed at Freddy Fazbear's Pizza.
However, at night, he acts as the other animatronics do: hunting down any human in the area and forcefully stuffing them into a Freddy Fazbear suit, killing them.
Bonnie is the only anamatronic to start at night 1, which makes him different.
People normally question Bonnies gender, but we now know Bonnie is a boy.
Bonnie is fast and aggressive, but easy to detect and stop. Bonnie only comes to you from your left side.
It should be noted that Bonnie does not attack once it enters your office. When it is inside, it will attack after you view the tablet. One way to tell is that your door and light switch will be jammed, then you know that Bonnie is holding the switches in the shadow.