NOTE: Although it is rare, a folded ear kitten can unfold and an unfolded kitten can fold up to 6 months of age.
According to Wikipedia, the original Scottish Fold was a white barn cat named Susie, who was found at a farm near Coupar Angus in Perthshire, Scotland, in 1961. Susie’s ears had an unusual fold in their middle, making her resemble an owl. When Susie had kittens, two of them were born with folded ears, and one was acquired by William Ross, a neighbouring farmer and cat-fancier. Ross registered the breed with the Governing Council of the Cat Fancy (GCCF) in Great Britain in 1966 and started to breed Scottish Fold kittens with the help of geneticist Pat Turner. The breeding program produced 76 kittens in the first three years—42 with folded ears and 34 with straight ears. The conclusion from this was that the ear mutation is due to a simple dominant gene.
The rare distinctive physical traits of the breed, combined with their reputation as unusually loving companions, make Folds highly sought-after pets and Fold kittens typically cost considerably more than kittens of more common breeds. Scottish folds are also popular among celebrities.
All Folds are born with straight, unfolded ears, and those with the Fold gene will begin to show the fold usually within about 21 days. The kittens that do not develop folded ears are known as Straights. The original cats only had one fold in their ears, but due to selective breeding, breeders have increased the fold to a double or triple crease that causes the ear to lie totally flat against the head.