Episode 157
On the way to the Battle Pike, Ash and friends stumble across a ninja school. However, there have been thefts around the school lately and they are told to be alert. On one of their tasks, which is to find the teacher's Kecleon, Ash and another Ninja stumble across a Bonsly. Bonsly is quickly blamed for all of the recent thefts at the school but Brock quickly proves them wrong. Soon after, the real thieves, which is none-other than Team Rocket, show up to steal all of the Pokémon at the Ninja School!
Aired 15/12/2005EP 157 - Episode 157
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)