Do you know if there are any characters that use multiple sets of Pronouns?
there are! in fact, quite a lot of utdr characters are referred to with multiple sets of pronouns:
chara uses they/them and it/its pronouns
the ruins dummy uses they/them and it/its pronouns
loox uses it/its and he/him pronouns
snowdrake uses he/him, it/its, and they/them pronouns
lesser dog uses it/its and they/them pronouns
gyftrot uses it/its and they/them pronouns
greater dog uses it/its and he/him pronouns
so sorry uses they/them, it/its, and he/him pronouns
knight knight uses it/its and she/her pronouns
endogeny uses it/its and they/them pronouns
snowdrake's mom uses she/her and it/its pronouns
lost soul papyrus uses he/him and it/its pronouns
lost soul sans uses it/its and he/him pronouns