A Fnaf theory of my own.

After taking a quick look at both the endings and the Easter eggs, i have a few theories.

I think that the kid you're playing is the one who'll eventually become Golden Freddy, as he was bitten and not stuffed in a suit. I believe he takes the form of Golden Freddy because its the closest to Fredbear he could get. And "what he has seen" that the voice keeps telling him. What if he's terrified of the animatronics because he saw the spring suits kill the two employes (who would eventually become Shadow Freddy and Shadow Bonnie) and is traumatised because of it? Another thing: on his way home on the third night, he passes by 4 kids making fun of him, and seeing as he's always there and has toys of the animatronics, its safe to assume his father works there.
I think he's the kid of Purple Guy. Think about it: To a parent, nothing is worse than loosing his son. And after it happened, i think he started going insane and decided to, one by one, kill the other children who made fun of him either one by one or all at once. And if he killed more victims (or not. Nobody has proven that) that's because he has become a psychopath, having given in to his rage. Until he was eventually chased by the ghosts and killed in the Springlock suit.

Now a lot of people say that it can't be 87 because of the 83 tv easter egg... I find this argument unreasonable. Many companies usually put the year they were founded beside their name. And since it says "Fredbear AND FRIENDS", then it makes sense how Freddy, Chica, Foxy and Bonnie were all there as toys and plushies. They're all a franchise. I think the bite was what caused Fredbear to be scrapped. If someone is killed by the spring locks, you just never let them use the suits as, you know, suits. But if the animatronic itself kills someone, its unsafe.

In other words, i think this kid is Golden Freddy and was the cause of Purple Guy's rampage on children.

(Sorry for the poor grammar. I uploaded this in a bit of a hurry before i have to go to bed early)