The Crimson Binome
Hero
Yes? I mean, at this point, D&D is a reflection of itself. Everything in the Monster Manual is... everything from the most popular Monster Manuals from previous editions.Have you seen the Monster Manual?
Can you count all the other games, the mythologies, the novels and the short stories, which inspired its monsters, on the fingers of one hand?
Once, long ago, vampires and werewolves were different legends. By now, they are inextricably linked such that the presence of one (in any given media) practically guarantees the existence of the other. It's all just generic fantasy by now. Mummies, golems, orcs, goblins, vampires, sphynxes, manticores - all generic fantasy.
Furries aren't quite generic fantasy yet, though. You can't assume that D&D must allow furries, before they release a supplement for it. And we're not playing GURPS, where you can build anything - D&D includes a lot of very specific stuff, but the things that aren't in there (like furries), just aren't part of the game. A bear using martial arts is entirely out of genre for D&D.