On their journey, Ash, Serena, Clemont, and Bonnie come across a Gourgeist Festival, where everyone dresses in Pokémon costumes. Naturally, our heroes want to join the fun!
Meanwhile, Team Rocket, also in costume, gets an invitation to the castle from Count Pumpka. His Prince Pumpkaboo has developed quite an interest in Jessie’s Pumpkaboo. Jessie seizes the opportunity and tells the count that some terrible villains have stolen her Pikachu—namely, our heroes! She suggests that she might trade her Pumpkaboo to the count if he helps rescue Pikachu.
The count’s steward confronts Ash and the others, demanding that they return Pikachu to its rightful Trainer—but because Pikachu is wearing a Psyduck costume and Chespin is dressed as Pikachu, he ends up grabbing Chespin by mistake!
Back at the castle, Jessie reluctantly agrees to the trade. But when the trade is complete, Jessie’s Pumpkaboo evolves into a Gourgeist, and suddenly Prince Pumpkaboo isn’t interested anymore! Jessie gets her Gourgeist back, Team Rocket is revealed and promptly sent blasting off again, Chespin and Clemont are reunited, and all’s well that ends well!