From Bulbapedia, the community-driven Pokémon encyclopedia.
The Croagunk Festival (Japanese: グレッグル祭り Gureggru Festival) is an annual festival located in the Great Marsh celebrating the Pastoria City's mascot, Croagunk. It was prominently featured in Cream of the Croagunk Crop!.
Ash and his friends were invited by Crasher Wake to go to the Great Marsh. There they encounter several Croagunk with their Trainers going to the main venue of the Croagunk Festival. Vendors line the area in the Great Marsh selling food, along with other items. The event features a test of strength and a beauty contest, where the Croagunk who pass the test, face the champion from the previous year. The winning Croagunk is rewarded with a crown with a diamond and a pearl. The judges of the competition are Carny, Nurse Joy and Crasher Wake. Brock enters with his Croagunk and Jessie with Meowth disguised as Croagunk.
Brock wins all the events to face Hamilton and his Croagunk nicknamed Craig, the defending champion. Team Rocket interrupts the fight, stealing all the Croagunk in the process. However, Nurse Joy and her Croagunk named Chrissy save the day with a Vacuum Wave. Everyone agreed that Nurse Joy and her Croagunk will be the champions of the festival and a party ends the festival.