Spoink, the Bounce Pokémon. Spoink bounces about on its tail. The pearl upon its head helps to magnify its psychic powers. If a Spoink loses its pearl, it grows extremely tired.
– Ash’s Pokedex
Spoink’s Pokedex entries all say that bouncing on its tail keeps its heart beating, therefore, if Spoink stops bouncing, it would die. I wonder what happens when it sleeps though, I guess it’ll just keep bouncing? The pearl on top of Spoink’s head is removable (ie not part of its body), as seen in the anime. It apparently boosts its psychic powers, and it’ll be very sad without it.
Spoink’s shiny sprite is a reversed colour version of its normal sprite; the pearl is grey while the body is pink.
Stat-wise, its highest stat is in Sp Defense, but its Sp Attack and HP are pretty good as well.