• English / United States: Ash's Sewaddle
• Japanese / Japan: サトシのクルミル
• Japanese (Romanized) / Japan: Satoshi no Kurumiru
• Japanese (Trans) / Japan: Satoshi's Kurumiru

While traveling through the Yaguruma Forest towards Castelia City, Ash Ketchum encountered a Sewaddle that attacked Pikachu with String Shot. It later attacked Ash Ketchum as well but just as Ash Ketchum tried to capture it with his Poké ball, it escaped. Ash Ketchum decided that he still wanted to capture it as it showed a feisty fighting spirit which Ash Ketchum liked. He decided to follow it into the forest.

After finding Sewaddle in the forest again, Ash Ketchum showed Sewaddle that he was a good trainer by rescuing it from a surprise Woobat attack. Ash Ketchum tried to rescued it again after a Patrat attempted to capture it but just before Ash Ketchum showed up, Sewaddle managed to get its String Shot stuck to a passing Shikijika. It fell off a cliff into a raging river towards a waterfall but Ash Ketchum went in after it. They were both rescued by Burgh's Leavanny and Burgh's Leavanny made a new leaf backing for Sewaddle.

Sewaddle gained Ash Ketchum's trust and was then allowed itself to be caught in a Poké ball but as Ash Ketchum tried to recall it after being captured, the Poké ball wouldn't work as Sewaddle was his 7th on hand Pokémon. Ash Ketchum decided to keep his Sewaddle on his team at that time for training.

Ash's Sewaddle evolved into a Ash's Swadloon during the gym battle with Burgh.