Misty's Staryu (Japanese: カスミのヒトデマン Kasumi's Hitodeman) was the one of the three original Pokémon acquired by Misty in the Kanto region. Its voice actor in both Japanese and English is 三木眞一郎 Shin'ichirō Miki.
Misty uses Staryu often as one of her main attacking Pokémon throughout most of the series. It doesn't seem to have much of a personality due to its extremely un-anthromorphic features, but Misty says she's able to recognize its emotions and feelings.
Misty used Staryu quite often in Kanto and during the Orange Islands saga. However, after she captured her Poliwag, she started to use it less often. By the end of the Johto saga, Misty hardly ever used Staryu, preferring to use her Corsola and her Politoed.