#greggory

Essentially I believe that David and Fiona didn't move on and that Fiona is in the body of the M-1 mimic and David is in M-2 at the end of the game, but is no longer in M-2 when we get to Security breach/ruin. I think there are too many elements of David that tie directly and completely to the crying child to just ignore it, and like MattPatt says I think there are too many ties between the crying child and Gregory to ignore as well. Plus, the weird way Gregory acts in security breach and us still not knowing how he got there, I think all of that has to do with David and the secret of the mimic.

First of all I do think that the mimic storyline is a combination of soul possession and AI. Which is a much more satisfying story when compared to the original FNAF games. I think that when Edwin heard Fiona is the basement he wasn't hearing the mimic mimicking her, I think it was actually her. The people who argue that that was just the mimic and not her soul mostly make this argument on the idea that the line spoken by the spirit is one she said in one of the videoes (that he's missing the party) yet we know from other clues and the lack of a tape that Edwin missed David's fourth birthday (Tom explains that a bit in the Game Theory Video on this). I think that Fiona was seeing David play alone with the costumes in the manor without his father beside him for his birthday and she wanted him to realise that he was abandoning their son when he needed him. It is a repeated line, but it's because he is still doing the same now as he did then. It's also that emotion that allows her to finally get his attention without a body. I still haven't figured out what exactly tethers her to the Manor given that she died at Fallfest but given that the manor is where her family is it's not hard to believe that she was tethered there.

Mostly I agree with/like this theory which points out the fact that Mattpatt's Gregbot theory was on the right track and I'm not going to repeat everything from it but mostly I agree, except for the questioning of how David's spirit got into the crying child.

I think when we see the ghostly apparition of David's tiger, which represents David/the mimic in the book, we are encountering David's ghost. The reason that Edwin couldn't get the M-2 program to work was that David is a child and didn't understand how to possess the new body. Fiona hoped that if she was removed and they used the same body her lifeforce plus the empty code would call David to it. When the programing was moved into M.X.E.S. her soul was as well, leaving the mimic program without a soul to control it, and leading it to it's violence. When Arnold tells the Mimic the bedtime story with the plush-- which I believe David's soul is tethered to-- on top of the controls, the mimic is fixed and David's soul is taken from wandering through MCM and into the mimic itself. And I think this is the real ending of the game.

David is left in the house when Arnold leaves. When Afton and his family move in David is still there. They move in in 1979 and the crying child dies in 1983. We don't know how old he is 1983, but it's only 4 years later. My personal guess is that he is about 10 given what we know about him, which means that when they moved in-- if they move in right after the events of Secret of the Mimic now that M-2 is not a danger-- then that would mean that the crying child would be the same age that David was when he died. It makes sense that David the mimic would want to make friends with him. Afton then moves the mimic to the bunker (built underneath the old Manor our of Edwin's old bunker which means yes that was the actual FNAF four house overtop of the bunker and not a rebuilt version of it as some people speculated in Sister Location), but the crying child is friends with him. He sneaks out his window in the same way that David (who we know snuck out of the window from moon.exe) taught him how do a meets him in the bunker. (he's headed off to "that place" again, plus the 3-toed animatronic footprints outside of his window, left by the M-2 endo). Afton then locks the mimic away underneath the manor, but before he can David, scared of the dark and being alone, jumps off of the endo skeleton and latches on to the crying child. When he's talking with Cassidy in the notebook, he's uncertain of things about himself and what he remembers because the soul of the crying child and the soul of David are combined together. When Cassidy asked him if he remembers his name he does answer "Dave" or "David" not because he and the crying child have the same name, but because they have become David.

When the crying child moves on, David stays latched to one of the arcade games, not wanting to move on. That game's parts end up getting repurposed into the Balloon Boy machine which is glitchy and annoying so no one plays it, until Greggory (or GGY) who wants to have the top score in all of the arcade games. He determines to finish the game. When he does, David enters him.

And well the rest of that lines up with the theory. In Security Breach David/Gregory is working with Fiona to keep the now not-possessed and so no-longer docile endo skeleton of the mimic from getting out and hurting people.