Yes even I've gotten caught up in the FNAF craze.
I'd thought I'd join in on the fun and add my own interpretation of the likely insane protagonist, and my own explanation:
Ten years after the five kids were murdered, Mike Schmidt, the younger brother of one of the victims, decides to take a job as the night guard at the infamous Freddy's Pizza, sneaking out every night to investigate the pizzeria. However it quickly goes awry when he discovers the whole "killer animatronics trying to murder you dead thing."
However, although every sane part of his brain is screaming at him to leave and never come back (or get a priest), something he can't explain compels him to return every night, hoping beyond hope that he can solve the mystery of his brother's death from the claustrophobic safety of the security room.
Is it really just shitty programing?
Are the animatronics malicious?
Are they possessed? By demons? By the murdered children?
If it's the murdered children, which one's his brother...
And where's the fifth child?
This drawing is actually the start of a comic I'm working on, which takes a couple of the headcanons I've seen that I like and sort of smooshing them together to make something my own.