First mentioned in season 1, Brennan has a love of dolphins, which she shared with her late mother: in the season one finale, "The Woman in Limbo", Brennan examines a custom-made belt with a dolphin on the buckle, which had belonged to her mother, and which she mentions having once borrowed without asking first. Brennan's love of dolphins has highlighted again in season 2 episodes "The Titan on the Tracks", "The Killer in the Concrete" and "Stargazer in a Puddle", when she mentions the constellation Delphinus, (the Dolphin), her and her mother's favorite. In season 6, "The Doctor in the Photo", she is shown to wear a dolphin ring.