Episode 180
On the way to Indigo Plateau for May’s Grand Festival, a group of Aipom come by and steal Ash’s hat and May’s ribbons! A old man comes by and tells them that local Aipom, Mankey, and Vigoroth have been stealing his berries and taking them up to the mountains. He also tells them that there is a rumor about a giant monster living in the mountains. They follow the Aipom into the mountains to a giant wooden fence. When the fence opens up, they run in and find out that it is really a Giant Slaking working with Team Rocket! They plan to use all the berries to make and sell Pokéblock at the Grand Festival, and Jessie will use May’s ribbons to compete! After being chased out of the Slaking’s territory, Ash and Brock are separated from everybody else, along with the Aipom that stole Ash’s hat. Can they reunite, get May’s Ribbons back, solve the mystery of the Giant Slaking, and get Ash’s hat back?
Aired 08/06/2006EP 180 - Episode 180

Pokémon the Series: Ruby and Sapphire
After participating in the Johto League, Ash decides to begin anew in yet another journey; this time by himself and Pikachu, in the land of Hoenn. Though he isn't alone for long, as 10-year-old May (who dislikes Pokemon, but just wants to come along to see the world) travels with him after Pikachu destroys her bicycle. Ash also meets up with his old companion, Brock, and May's younger brother, Max. Together, they travel along in Hoenn, battling Gym Leaders, entering Contests, and other events on the way to the Hoenn League.
(Source: Anime News Network)