In Kanto at six o'clock, you can find dancing Clefairies on Route 4 (Outside Mount Moon), but only on monday nights. They are in the patch of grass with little flowers. When the Clefairies notice you, they run away, but they will leave a rock that one of your pokemon can rock smash and under that rock is a moon stone. Which can evole pokemon like Nidorino and Clefairy.