Once in a Blue Moon

Ash and friends arrive in Cherrygrove City where they have an encounter with a Quagsire. It steals the GS Ball and runs away. Officer Jenny tells them that the Quagsire do this every year on the night of the blue moon. Not wanting to wait for the GS Ball to float back down the river, Ash, Misty, and Brock follow the Quagsire up the river.