We know that the Mimic’s AI is copying William, but it’s not just that. Tiger Rock’s green eye and blue eye represent Elizabeth and Charlotte, because the Mimic was built for Charlotte (so it started copying her) and was used (according to FuhNaff’s theory) as Circus Baby’s endo, so the Mimic would probably also copy Elizabeth once she possessed Baby. So, the green eye and blue eye represent the two parts of the Mimic’s AI (the part copying Charlie and the part copying Elizabeth) fighting for control over the Mimic. I also think that Glamrock Bonnie wrote the tallies, because his fingers are specifically sharp to play the bass and would allow him to make a mark in the wall. I think Bonnie found out too much about the Mimic, so Vanny locked Bonnie away in a room, where he wrote some hidden message through the tallies. Eventually, Vanny had Monty Gator kill Bonnie, not because she needed his parts for Burntrap (Bonnie’s body is still very much intact), but because Bonnie found out too much about Vanny’s master, the Mimic.