The question Centaurs, do they have control of their bodily functions?Centaurs, do they have control of their bodily functions? asks what I consider to be a legitimate question (albeit containing misconceptions about real-world zoology) about a fictional species that appears in RPGs.
Are questions about species appearing in roleplaying games that require research outside the rules in the specified RPG system on-topic?
EDIT:
To address Brian Ballsum-Stanton's comment regarding the meta question Are campaign research questions on topic?, Is this sort of question campaign research, which that Meta question's consensus appears to suggest is on-topic?