Cases of polydactyl cats are not infrequent , so maybe not far fetched for multi eared ones; there are afterall recorded instances of two headed snake, calves, goat, etc.
But your reactions are interesting in a C.S. Lewis fashion. With the prevalence of photo shop and snap chat filters, CGI movies, an entire generation has come to false images as ho-hum and not at all remarkable.
Current culture mores seem to indicate that demons and the ant-Christ could appear uncloaked in light and be thought of as “cool”.
Pyewacket, the feline familiar from the movie “Bell, Book, and Candle”, 1958, being a an evil Siamese was obviously a creature of the under world, why not this smoky cat.
I don’t see why a cat with four ears would be any more demonic than the average one. Don’t they all work for the other side in various ways?
During the Salem witch trials, one woman was convicted because only a witch would name her cat “Pyewacket”.