Mounts/non-humanoids as PCs; are there any official/fan-standard rules?
You get the idea, right? There's lots of sapient animals to ride on in fantasy fiction, but are there any rules for playing one in 5e D&D?
I remember vaguely from Races & Classes (back in 4e) that the idea of adding talking animals as a playable race was seriously considered, but they couldn't get it to work within that ruleset...
Actually, what are the rules for one PC riding on another? In the case of wild shape or polymorph or whatnot? And what are the rules for dextrous acts and fine manipulation when you don't have a normal pair of hands?