Freddy Fazbear

Freddy Fazbear is the lead singer of the animatronics band in Five Nights at Freddy's.

Freddy caused The Bite of '87
This theory is one of the most well known theory, before FNAF 2. The main evidence for this theory is the handprints on Freddy's face. Also, Freddy was in free-roam in the day, and his mouth is big enough to bite off a frontal lobe.