Crystal Bits are jewels that belong to Crystal King. They assist him during battle with Mario. They can be destroyed quickly with a multi-hitting attack, like multibounce or Thunder Rage. Crystal King can summon them several times throughout battle, using up a turn.
Although they are easily killed, it is more advantageous to leave them alive. If they are killed, Crystal King will shoot a bolt of ice at Mario, dealing 8 damage and possibly freezing him. If properly defended against, the barrage of Crystal Bits can do significantly less damage.