I remember the first time I ever heard a cat purr. I freaked. I didn't grow up in a "cat house" (no, not that kind either!), so I didn't know what it was. I thought something was wrong with the animal. Warren still sometimes thinks something is wrong when Lady is making "doggie love noises" and often mistakes it for sneezing.
Years ago "Mystery Science Theatre 3000" created a robotic "dog" named Nummy Muffin Kookle Butter. They had it making very soft noises. When I realized those were "doggie love noises," I fell on the floor laughing. This was when I realized "doggie love noises" were just as universal as purring.