That's a big question too, because we'd have to determine if a fursuit is merely a creature costume, a personal expression or a specific pattern of suit. There are fullbody animal suits from the 1800s ! But from my knowledge those are for theatre plays; and then at that point I'm sure we've been reenacting animals until the dawn of time. I wonder if the requirement is "someone's fictional character", specifically, but then that gets tricky in its own right because the only line we have for mythos vs fictional characters nowadays is copyright. (us contributing hatsune miku as a deity of creation for even things she hasn't done is not so unlike how greek heroes could be a mixture of stories and historic events by various people merged under a single credit, the things we're missing is context that got lost to time, how would people see hatsune miku in a thousand years if half of us context was lost?) Which isn't to call mythos fiction, but to say that I guess it's hard to know the relation the people wearing the suits would have to whatever they're portraying without lived context. These are a lot of big thoughts GHKG