So, we've all heard the theory that Phone Guy is the Purple guy because of the 8-bit pruple character holding something that looks like a phone and wears a badge, nooow I want to disagree with that theory, and here's why.
In the minigames at the end of each night of Five Nights at Freddy's 3, we can see Purple guy and the 4 animatronics in the 3rd Restaurant aka, Five Nights at Freddy's, and we could argue here that when Phoen Guy dies night 4 of the first game, he becomes Springtrap? Yes? Possibly, however may I remind you that the animatronics are still intact when we play as Mike Schmidt, and from what we can gather of the minigames is that the animatronics get dissassembled by the Purple Guy, releasing the sprits to haunt him.
Now this has had to happen after the events of the first game, after the place was shut down as Purple Guy always returns, what I'm saying is that Phone Guy, cannot be Purple Guy, and he couldn't even fake his death because I'm pretty certain the animatronics would not just play a long nicely like that.
But if it's not Phone Guy, who then? Well, there's two other characters that we know for certain *are* alive, Mike Schmidt and Fritz Smith, we don't know what happened to Jeremy Fitzgerald but he could've possibly been a victim of the Bite of '87, so he's out of the question. So that remains us with Fritz Smith and Mike Schmidt, what else is worth noticing is that in contrast to Purple Guy in Five Nights at Freddy's 2 where he's wearing a badge, in the minigames of FNAF3 he's not, which means that Purple Guy does not work at the pizzeria anymore, now we don't know what happened to Jeremy, Phone Guy is dead before the game ends so it leaves Mike and Fritz, and both of them get fired at the end of Night 7/ Custom Night for Tampering with the animatronics and Odor, making them both the suspects.
Because Fritz Smith was a character filler to replace Jeremy night 7, we could exclude him from the picture, so it leaves Mike, now we don't know Mike's past, he could've worked at the pizzeria before, as a different member of staff, even as a day guard and then Night Guard at the last pizzeria, and if we notice if Mike dies in the game, he is stuffed yes? But we don't know what happens to the other animatronics either, and if Scott follows the Vengeful spirit rules, (which he probably does) it'd mean that after Purple Guy gets killed, the spirits would leave, and because we don't know what happens to the animatronics, we can assume either they rest or they continue searching.
Soooo, yeah, this is my theory on who Purple Guy is, probably going to get hate for saying the lovable Mike Schmidt is Purple Guy, but it makes sense.