The question [Centaurs, do they have control of their bodily functions?][1] 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?][2], Is this sort of question campaign research, which that Meta question's consensus appears to suggest *is* on-topic?

  [1]: http://rpg.stackexchange.com/q/39545/8962
  [2]: https://rpg.meta.stackexchange.com/questions/570/are-campaign-research-questions-on-topic