Pokémon: The Series Rewrite:Indigo League Part 1

Episode 4: Showdown In Pewter City

Ash and Misty arrive in Pewter City where Ash plans to have his first gym battle. Ash decides to have a battle with the gym leader Brock who uses a Geodude and Onix while Ash uses Pikachu and Pidgey. Pidgy takes down Geodude but is knocked out by Geodude leading to Pikachu vs Onix which fails because electric types don't affect ground types. Ash looses and goes to sulk when he meets a old man who helps him train his Pikachu and Pidgey helping Pikachu learn Thunderbolt. Ash has a rematch with Brock leading to Ash winning by using the sprinkler system. Ash gets the badge when the old man who is revealed to Brock's dad who takes over the gym. The episode ends with Brock deciding to join Ash and Misty on their journey.