My cat would have been from a shelter, but I claimed him first. 🙂
A few years ago, a friend who lives on a farm found a stray cat wandering. Lots of people tend to leave their unwanted cats and kittens around farmland and this wasn't the first cat she had found on her property. The cat took to her and liked her, so she decided she would keep it. Took it to the vet to get the cat checked up and desexed, only to find kitty was pregnant!
She looked after the cat whilst she was pregnant and looked after the newborn kittens too, and was going to take the kittens to the animal refuge once they were old enough... on the week she was going to take them into town, I took one of them.
Unfortunately stray cats and overbreeding is rampant where I am too.
They're trying to cut down on it though. For example, pet shops are not allowed to sell cats. Only registered breeders are allowed to breed and sell cats. The only other avenue is from animal shelters. You will not find any classifieds listing saying that there are kittens available; it's just not allowed anymore.
RE: Cats are overpopulated - Why adopt cats from shelters?