@Felthry Not so weird, actually. A number of North American languages use various deformations for the speech of certain mythical animals, e.g. in Hupa, when Frog is talking, s is replaced with sh. I'm pretty sure there are other languages where there really are grammatical markers for specific characters speaking, but I can't find any references right now.
@Felthry The latter, yes, but [language feature used only by specific characters] is a thing, and it's not a stretch to imagine that some language goes further and, say, uses alternatives words or markers, or even introduces new markers - and I'm sure I've read of languages that do do this, I just can't remember what they are. Languages do even weirder things than this, after all.