Interestingly Starmie's "back-half" has been depicted several different ways. In the anime Starmie has the appearance of two starfish fused together; while in more modern games the back-half has been shown to spin wildly completely independent of the front-half of the Pokémon. Many fans tend to think of the anime's depiction as the more realistic of the two, considering the rapid spinning would obviously get in the way of any trainer trying to surf on this particular Pokémon. Starmie's core shines in a rainbow of seven colors, some people value this core as a type of jewellery.
Starmie gains three abilities, which are Illuminate, Natural Cure, and Analytic (obtained via Dream World). Illuminate increases the chance of encountering wild Pokemon. Natural Cure removes any status conditions when Starmie switches in and out of battle. Analytic allows Starmie to gain a boost in its attack stats if it is slower than the opposing Pokemon.
Starmie is able to emit peculiar signal waves from the gem-like core attached to the center of its body. These waves are said to cause headaches to those who get near Starmie (according to the Pokemon Sun Pokedex entry). The core radiate the seven colors of the rainbow, earning the nickname “gem of the sea”.
In the anime, Misty owns both Starmie and a Staryu at the same time, making it one of the extremely rare cases that a trainer has both pre- and post-evolutions on their person at the same time. She later gave away Starmie to the Cerulean Gym to preform underwater shows, but kept her Staryu.