Theory , definitely can be wrong

Okay theory time!

I think Fluffy was one of the first to get involved in transferring into a humanoid animal , at least at the farm(in a chapter its mentioned that Fluffy has been there the longest, and why some think hes Mr.A's son but by now we all know that Fluffy was dead ass just his dog.) And I think what was in that box was like a drug that transforms people into the creatures, and maybe Fluffy licked that shit or sum, or Little A was playing in it- idk I need another chapter with da box. The transformation is happening all over the country, but its only a few years old. Little A looked to be maybe 10 or so in the flashback and now hes a young adult so I think hes 19-23 so makes sense... (someone else use ny brain to think)

It could be possible that someone else wrote Little A the letter in the first place because his uncle signs his name off with just his inital. Idk if Mr.A does that normally, but it would make sense if someone posing as Mr.A wrote the letter and because of the rules, had to use the inital because Mr.A himself seems to be unaware and he's also transforming himself (if you look at his hair, there's fluffiness by his ears)

I *think* they invited Little A because they needed someone to help ease the mind of the other humans (or whatever theyre called. Furries...idk man) and I don't think the Doctor who sent it since the guy was willing to kill Little A (or, maybe turn him into a furry too teehee...) so Im rolling towards maybe the pink guy (the pig) sending the message since he seems to have a higher position than the other farm animals (he's always with the Doctor from what we saw, although he got his shit beat in)