Delta hearts

Like dumb theory with the keys. Like in game its revealed that the keys made the scaries stronger, and angrier though blue prints in the game shown that it says it removes consciences and not put you control. and since wind up keys are usually for different wind up toys the headmaster could be controlling the 3 scaries like they are his toys.

Should add that fact could be confusing to why Mary and Barry would put on the keys my guess is due to the fact Mary is shown to be scared of the headmaster and shown saying the headmaster will be mad if she doesn't complete his design in time. plus with the notes she might not even be sure if the key actually does remove consciousness which is why she wanted to test subject.

She likely just saw how Larry didn't immediately drop dead and was still conscious she decided that the project was a success without going into further testing with the added fact again the headmaster gave her a deadline.

also another fact people know about with Brooke and Luke. While mostly shown with Brooke in her origin ending design it Kind of looks like they got legs of arms that of a doll so the two are probably some sort of sentient dolls which could add to the whole toy theme some of the bosses have going on if the wind up keys be taken literally.

(added fact even though roblox break in is a cartoony, the two do got orange cheeks. and they don't look natural)

So yeah that my theory. The headmaster just puppets the scaries and the twins like they are his toys.

Break in 3 could ether make or break this theory with how in the normal ending which is probably the canon one. Larry's key shown gone.

Like if he reverts back to his shy and awkward personality that is one thing but added fact if the key does remove conciseness he might not even have any memories of what had happened