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Although the gem on the end of its tail is quite heavy, Starill's psychic power is strong enough to roll it like a ball. It's often seen bouncing happily with a twinkle in its frontal gem as it rides around on its tail.

Its tail, which is packed with nutrition, is very bouncy like a rubber ball. People in ancient times imagined that Starill were transformed from the reflections of stars that twinkled on gentle waves at night.