This leads into a whole other field of study, should one be so inclined, and that's to go through the Monster Manual, find all the cross-breed races (e.g. Tabaxi is part human, part cat), and then from there figure out what can in theory breed with what and-or have what in its bloodlines. Can, for example, a half-orc breed with a half-elf and produce an offspring that is genetically 1/4 elf, 1/4 orc, and the rest human?
I did this a long time ago using 1e's MM, FF, and MMII; and the results were rather staggering: a chart on a big piece of paper with lines connecting inter-breedable races that ended up looking like a plate of spaghetti. And that's before throwing in things like shape-shifting deities (consider the myths of deities like Zeus and Loki impregnating humans), demons, devils, and the like.
Ever since then, every character rolled up in my games gets a roll during char-gen to determine if there's anything unexpected in its bloodline - are you, for example, a distant descedant of a deity...or a devil, or an orc, or a cat...
So, back to topic: peeved that nobody, either in official D&D or a 3rd-party, has ever published anything like this even as a magazine article.