courtesy of Wikipedia: "Cats in StarClan are restored to the age in which they were happiest, for example, Yellowfang is old, because she was happiest at the end of her life, when she was in ThunderClan and Bluestar is young, because she was happiest at the peak of her youth. They also do not age in StarClan. Cats who die keep their name at the highest rank they had or would have achieved; Smallkit, for example, becomes Smallstar, as had he survived longer he would have become leader."