From Bulbapedia, the community-driven Pokémon encyclopedia.

The Advanced Generation series (Japanese: ポケットモンスター　アドバンスジェネレーション Pocket Monsters Advanced Generation) is the second series of the Pokémon anime. As the previous three regions that Ash Ketchum had traveled through were part of one series, the beginning of this series came as a surprise to many.

In this series, Ash is joined not by Misty, who had been his continuous companion for the entirety of the original series, but May, a rookie trainer from Petalburg City who merely wishes to travel at first. Eventually, she learns of Pokémon Contests and declares herself a Pokémon Coordinator. Brock, Ash's near-constant adviser, returns soon after the start of the series.

Another change in this series that surprised many was that of both Ash and Brock's clothes. No longer did Ash wear the hat he claimed to have sent in a million postcards for, but instead a completely different outfit.

The Advanced Generation series saw a change in the formula followed by the original series, as well. While in Kanto and Johto, Ash encountered all three of those regions' starter Pokémon and caught each. In this series, however, Ash's only capture of a starter was Treecko. Also, unlike when he traveled to the Orange Islands and Johto, Ash left behind all of his Pokémon at Professor Oak's, bringing only Pikachu.

When the Advanced Generation series came to be dubbed into English and other languages, it was divided up into four seasons:

• Pokémon Advanced (AG001 - AG040)
• Pokémon: Advanced Challenge (AG041 - AG092)
• Pokémon: Advanced Battle (AG093 - AG145)
• Pokémon: Battle Frontier (AG146 - AG191)

Episodes in the Advanced Generation series are numbered with the prefix AG. For a complete episode listing, see the list of Advanced Generation episodes.