Staryu’s body is mostly composed of a pliable, golden-brown star-shape, from which Staryu derives its title as the Star Shape Pokémon. Between its five appendages, at the very center of its body, an exterior organ called the core is held in place by a gold piece. The core resembles a red jewel and functions similarly to a madreporite. Lopped around its left leg is a golden ring that seems to hold the core in place. Staryu is hermaphroditic.
Its core can be used to reflect and refract light and energy. This grants it the power to use moves like Power Gem and Light Screen.
The core of a Staryu acts as a heart for the Pokémon. It glows brightly when it is healthy and happy. When it is excited, scared or angered it will flash, increasing as the emotion intensifies. If a Staryu becomes weak, its core will grow faint and will also flash slowly when it is very sick or near death.
Staryu become most active at night. When the sun goes down the core will glow its brightest. Many will float from the seafloor to the surface and align themselves with stars of the night sky as their core flickers, displaying a connection with the celestial bodies of space.
Most Staryu can be found at the very bottom of the ocean on the seafloors. There are also many found in the waters of caves which are attracted by the dark, calm waters. There are times, however, when Staryu find themselves in rivers that lead into the ocean. Staryu will almost never be found during the day, when they are in the deepest parts of the ocean, but at night they freely move throughout the oceans' waters and even rest at the surface. They can be found throughout the waters of Kanto and Johto.
Like most Pokémon, Staryu's eating habits are unknown but it's very probable it filter feeds considering the Pokémon's lack of a mouth.
This Pokémon was unavailable prior to Generation I.