From the website http://www.catfacts.org/munchkin-cat-facts.htm:
Munchkin cats are a relatively new breed created by a random mutation that produced a cat with extremely short legs. Munchkin cats have short or long coats in a wide variety of colors. Because of this cat's short stature, munchkins are particularly adept at climbing and jumping. The Munchkin cat is usually raised as an indoor cat, although they are reported to be extremely active, agile and fast runners.