From Bulbapedia, the community-driven Pokémon encyclopedia.
The Bulbagarden Pokémon Anime Style Battling League originated on the Universal Pokémon Network forums in 2000.
The first Anime Style Battling association, BG PASBL was not initially popular when it first began, but was very active. The league had several unique features, including the concept of signature moves. These were special custom moves unique to each Pokémon owned by each trainer. The league remained on UPN until the site went down in late 2000. Soon afterwards, PASBL found a new home at Bulbagarden.
While at Bulbagarden, many of the rules were rewritten. This resulted in changes that remain in effect to this day. These include injuries, the ten-level system, league officials and official referees. Additionally, Generation II Pokémon were now allowed.