Pikachu and the other Pokémon are playing outside a cottage while their trainers rest, and Dedenne gets thrown off a roundabout, slips through an open cellar window and comes back up with a key stuck to its tail. Down among the stored pottery and furniture they meet Klefki, who holds the keys to the worlds where Mythical Pokémon live, and Chespin and Fennekin follow them in. This short played in theaters alongside the seventeenth Pokémon film.