• English / United States: Ash's Caterpie
• Japanese / Japan: サトシのキャタピー
• Japanese (Romanized) / Japan: Satoshi no Caterpie
• Japanese (Trans) / Japan: Satoshi's Caterpie

Ash came upon Caterpie while traveling through the Viridian Forest on his way to Pewter City. Instead of using Pikachu to battle and weaken Caterpie, Ash Ketchum just simply threw a PokéBall. Luckily, Ash Ketchum was able to catch Caterpie with no trouble. Ash Ketchum decided to let Caterpie stay outside of it's PokéBall and walk around with Pikachu; however, Caterpie quickly took a liking to Misty. Misty called Caterpie ugly and disgusting and informed Ash Ketchum of her hatred for all Bug-type Pokémon. Despite Misty's insults, he went to sleep next to Misty. After Misty insulted Caterpie once again, Caterpie cried and returned to it's PokéBall.

Shortly after, Team Rocket appeared and attempted to steal Ash Ketchum's Pokémon once again. Ash sent out Ash's Pidgeotto, but James's Koffing and Jessie's Ekans were able to defeat it. Ash Ketchum was then forced to use Caterpie, who was already tired from its previous battle with Ash's Pidgeotto. Its String Shot attack was able to stop Jessie's Ekans, James's Koffing and Meowth. Shortly after the battle, Caterpie evolved into Ash's Metapod just as Misty was attempting to thank him for his great job against Team Rocket.