Lily is one of Misty's three older sisters who lives in Cerulean with their two other sisters, Daisy and Violet. After Misty, Lily's the second youngest of the four sisters, and she often teases Misty about her being the youngest of the four sisters.
Lily's very cheerful and is shown to be the most childlike and carefree of her sisters. She loves shopping, wearing cute clothes and acting out roles in plays, but she doesn't like to do battles.
She wanted to play the role of the mermaid, and not a pirate, but when Misty left, she and Violet take turns playing the mermaid.
It apparently belongs to all four sisters. Participates in some water shows with the four. Evolves into Dewgong during a battle against Team Rocket.
The Sensational Sisters's multiple Goldeen inhabit the pool in the Cerulean Gym along with many other Water Pokémon. They first appeared in a water performance called "Underwater Ballet" swimming with the other Pokémon alongside Misty playing the mermaid, then pretend to go to sleep. When Team Rocket take over the show they get the Goldeen trapped in a net. In the end with the help of Ash and his friends including Seaking and Dewgong they are able to get the Goldeen free. It is later seen in the finale of the performance.
Three make a brief cameo in Cerulean Blues in the aquarium.