Brock is the first Gym Leader challenged in Pokémon Red and Blue.
Brock leads the Pewter City Gym in the Kanto region. In the original games, his team specializes in Rock-type Pokémon, and defeating him earns the Boulder Badge. He uses Geodude and Onix in Pokémon Red and Blue, making the battle an early test of type matchups and training strategy.
The player normally reaches Pewter City after traveling through Viridian Forest. A Pokémon such as Bulbasaur or Squirtle has a type advantage against Brock's Rock-type team, while Charmander faces a more difficult early battle. Winning also allows the player to use Flash outside battle after meeting the relevant later requirements in the original games.
Brock is also a major recurring character in the anime. He travels with Ash for much of the early series and later becomes a Pokémon Doctor. Misty is another famous Gym Leader, but she leads the Cerulean City Gym and is the second Gym Leader encountered in the standard Kanto progression.