Lilly is a small, plump, light gray tabby she-cat with big, milky blue eyes and a short tail.
Lilly is first displayed as a true kittypet: knowing each precise pellet-food flavor and loving her collar. She mentions her mother, Flower, and how she was killed by a car when Ginger is almost killed by one. At first, in contrast to her sister Bandit, she approves of Ginger and Gray's relationship. However, when she learns that Ginger is leaving with Gray, she is upset, but tells her littermate that is she knows her destiny, to follow it.
After the battle with SkyClan and Gray's group, she comes to SkyClan's camp in search of Bandit, who had joined the fight. She was crushed when she found her sister dead, but took the body back to the Twolegs so they would know what had happened.