I met a woman once who was obsessed with creating an eternal kitten. She collected petite cats and bred them, then bred the smallest cats she produced. I guess she was going for the tea-cup cat. As far as I know that woman did not succeed.
There are still breeders attempting to breed tiny cats. Have you heard of the minuet cat, a cross between a munchkin and a Persian (or Himalayan). Some call them the 
Napoleon cat. There’s also the Bambino (sphinx mixed with munchkin) for the hairless version of a small cat.
But the eternal kitten is just one type of cat serious and novelty breeders have attempted to create. As you know there are many new cat breeds showing up—some of them what you might call natural occurring.
Here’s a breed I don’t recall hearing about before. The Keetso. Keetso means big-footed in Navajo, which I thought was odd since this breed was first developed in the UK. The goal was evidently to create a cat with the temperament of a puppy. These cats have large feet like some puppies do—maybe that’s because they’re polydactyl—they have six toes on each paw. To top off their uniqueness, these cats have curly ears. It appears these big cats (up to thirteen pounds) may be hard to find here in the US. But when they are available here, expect to pay over $2,000. Check out the Keetso cat breed here: https://www.pets4homes.co.uk/cat-breeds/keetso/ (and elsewhere on the Internet.)
