History of the Sphynx cat:
Hairless cats have cropped up from time to time throughout the world as a result of this spontaneous mutation. The condition resulting in hairlessness is known as hypotrichosis which is caused by a recessive gene. Two hairless cats named Nellie and Dick were given to Mr and Mrs F.J. Shinick in 1902 by local Indians, these were named "Mexican Hairless cats". Other hairless cats have turned up in Australia, Europe & the United States. It is not known for sure if these spontaneous mutations are all the result of the same gene, three hairless conditions have been looked into, occurring in France, Canada and England, and symbolised by h, hr and hd, respectively. It is believed to be closely linked to the Devon Rex gene re. 
The Sphynx story began in 1966 in Toronto, Canada. A black and white domestic female by the name of Elizabeth gave birth to a hairless male kitten, named Prune. A local science student became interested in this unusual cat, and along with his mother Yania Bawa, a breeder of Siamese, obtained both Prune & his mother, Elizabeth. Prune was mated back to Elizabeth and this mating produced more bald kittens. A breeding programme was planned which involved mating these bald cats to American Shorthairs and the CFA granted these cats "new breed status", however by 1971 the status was revoked due to concerns over fertility. Unfortunately, these lines eventually died out.
The Sphynx of today is descended from four cats. Epidermis, Dermis, Paloma & Punkie.
A farm cat from Minnesota by the name of Jezabelle and owned by Ethelyn Pearson, gave birth to a bald female kitten who was named Epidermis. The following year Jezabelle had a second bald kitten, named Dermis. Meanwhile, back in Toronto, three more hairless cats occurred to the same queen, but in separate litters. Bambi was the first, a male who was neutered, then in 1979 & 1980 two females, Paloma & Punkie were born. These two cats were sent to Dutch breeder Dr Hugo Hernandez. Hernandez mated Punkie to Mewsi-Kal Starsky (who was from the original Canadian lines originating from Elizabeth/Prune). These matings produced no kittens, so Hernandez then mated Punkie to a Devon Rex named Curare van Jetrophin. The resulting litter produced five kittens. Two males from this litter (Q. Ramses & Q. Ra) were used, along with Punkie's half sister, Paloma. The descendants of these matings, along with the descendants from the Minnesota line (Dermis & Epidermis) went on to become the foundation cats of the Sphynx we know today.
Domestics, American Shorthairs, and Devon Rexes have been used in breeding programmes to increase the gene pool. The h gene is recessive, and in order for a hairless cat to be produced, it needs one copy of the h gene from each parent.
Appearance of the Sphynx cat:
As has been noted, the Sphynx isn't a completely bald cat but has a fine layer of peachy fuzz on the skin. Some hair may also be found on the extremities such as the nose, tail, ears & feet. Sphynx cats have no whiskers. Wrinkles are a desired trait in the Sphynx. Due to the minimal hair, the Sphynx feels surprisingly warm. The feel of the Sphynx has been compared to that of a chamois.
The medium-sized body is long but with great muscle definition. It has a deep chest and legs which are in proportion to the body. Hind legs are slightly longer than the front legs. The have medium sized, oval paws and a long, tapering tail.
Sphynx cats have huge ears, broad at the base. The head is wedge-shaped with rounded lines. There is a slight nose stop. The eyes are large and slightly slanting with the outer corners pointing towards the ears.
Every colour is found in the Sphynx.
Temperament of the Sphynx cat:
The Sphynx is an extremely outgoing, friendly and loving breed of cat. They love to climb and be up high, they have boundless amounts of energy & are always on the go. They have been described as "part cat, part dog, part monkey".
They get along well with people, including children and other pets. Due to their intelligence, they can be easier to train than other breeds, often learning tricks & happily walking on a leash. They do require a lot of company & shouldn't be left alone for long periods of time. If you are out for long periods of time, consider getting two cats.
Sphynx cats produce more ear wax than other cats due to the lack of hair. Regular cleaning will be required. Also, due to their lack of coat, they can be prone to oiliness and may need fairly regular bathing. Only ever use a shampoo designed for cats on your Sphynx. Human shampoos contain harsh chemicals which are not good for a cat's sensitive skin.
Due to their lack of coat, Sphynx cats should not be outdoor cats. If you live in a cool climate, make sure your Sphynx is kept warm, especially in the winter months.
Are Sphynx cats hypoallergenic?
No, the protein which causes allergies in humans is found in the saliva & sebaceous glands of all cats, including the Sphynx. Admittedly, due to the lack of hair, there is no shedding, but they still shed skin & peachy fuzz into the environment.
 Robinson's Genetics for Cat Breeders and Veterinarians - Carolyn M. Vella, Lorraine M. Shelton, John J. McGonagle & Terry W. Stanglein.