From Creatures Wikia
The first version of the Cat Norns were created by Mman and originally occupied Norn slot P. As the Bird Norns occupy the same slot, Mummy converted them to Norn slot Q. The female Cat Norn is based on the Desert Norn sprites, the male on the Emerald Norns sprites, while their genetics are based on those of the Golden Desert Norn. Only the sprites for the "baby" life stage were made and therefore the Cat Norns will stay the same size for their entire life span. They can be downloaded at Mummy's Creatures.
The new version of the Cat Norns were created by Alien as a part of aktion Pimp My Breed. Their sprites are based on the Desert Norn sprites and now sprites for the four main life stages are included. Since the original Cat Norns occupy the same slot as the Pumuckl Norn (C2)s, Phantom Norns and Ice Norns, the new version was written for Ettin slot U. They can be downloaded at Alien's Creatures World.