• English / United States: Ash's Treecko
• Japanese / Japan: サトシのキモリ
• Japanese (Romanized) / Japan: Satoshi no Kimori
• Japanese (TL) / Japan: Satoshi's Kimori

Ash's Treecko was first seen sitting on the withering old giant tree. It tossed a twig at Pikachu when it got close and then challenged Ash's Pikachu to a battle. The two battle for a bit until the older Treecko confronted Ash's Treecko and told it was time to move on to another tree. Ash's Treecko was born in the giant tree and it protected it as it grew up. As a sort of repayment to the tree, Ash's Treecko had been protecting the giant withered tree. Ash Ketchum realized after the battle with Ash's Pikachu and seeing it with the other Treecko, that this Treecko was strong and committed and he decided that he wanted to get it. Ash's Treecko is also known for its incredible speed as many people have noted that.

Ash's Treecko would make the long journey back and forth to get water for the withered tree to try to make it get better. Ash Ketchum and Ash's Pikachu decided to help it and started to gain its trust. After confronting Team Rocket, Treecko saved Ash's Pikachu and the other Treecko and went back to the giant withered tree just as it began to split in half. They all tried to rescue the tree but it was too late. An acorn dropped in front of Treecko just after it split and Ash Ketchum said that he believed that the tree was thanking it.

Pikachu vs Treecko

Realizing that its first home was now gone, Treecko challenged Ash Ketchum and Ash's Pikachu to a battle. Ash's Pikachu started off with a Thunderbolt but Max noted the Grass type Pokémon like Treecko are strong against Electric type moves. Ash's Treecko tried to use its speed to its advantage against Ash's Pikachu in the battle but it jumped into the air and Ash's Pikachu's Thunder weakened it because it couldn't discharge the electricity into the ground. Ash Ketchum then successfully captured Treecko.