FNAF?! I'M HERE I'M IN THIS LET'S TALK.
ok guys foxy is best animatronic

no but seriously there's a theory going around that foxy isn't evil and he doesn't want to kill you!
if you check the cameras too much, he thinks you're paranoid. but if you don't check them enough, he thinks the others have killed you, SO he runs to check on you. he also pops out of a corner, and not in front of you, because he doesn't want to scare you too much.
people think that this relates to the bite of '87, where in 1987 foxy accidentally bit off a child's frontal lobe, causing memory loss. he's really sorry for what he's done, so he tries to help you survive.
(WHICH YET LEADS TO ANOTHER THEORY)
Mike (the security guard you play as), is the child who got bitten by foxy! i mean, everyone else who heard about the bite of '87 never came back, but if the child's frontal lobe got bitten off (which causes memory loss) he wouldn't remember anything! thus, going to work at the pizzeria.
ONE MORE THEORY
why do you get payed so little? this job will give you $120, as it says in the newspaper. that pays for ALL the nights you work there (5). if you do some math, that equals up to $4 PER HOUR.
here's the math:
so you work 12am - 6am, right?
6 x 4 = 24, x that by 5 (the five nights) = $120
right now, it would be illegal to be paying somebody $4 per hour. BUT, if you think back to the 80's (87, 88, 89...) it would be legal!
that means that the game is set in the late 80's!
OK OK ONE MORE THEORY IT'S THE LAST ONE.
you aren't human. you're an animatronic! think about it... the light switch/door switches... you don't push them, YOU CONTROL THEM! the cameras... YOU WATCH OVER THEM! you're losing power over time... THAT'S HOW MUCH POWER YOU HAVE AS AN ANIMATRONIC!
(these are not my theories, but I think most of them are true)