Sewaddle first appeared while Ash and friends were in Yaguruma Forest. After attacking Pikachu, Ash tried to catch it but was not successful since Sewaddle ran away. It later reappeared and knocked Ash to the ground when the trio met Arti, the Gym Leader of the Castelia Gym, who revealed that Sewaddle was accompanying him through the forest even though it was not his Pokémon.
Sewaddle sleeping
Despite showing antipathy to Ash early on, Sewaddle started to change its mind about Ash when he jumped in front of it and took a Air Slash attack from two Woobat to protect it. Sewaddle and Pikachu then used a combo of Razor Leaf and Thunderbolt to scare the two Woobat away. Afterwards Sewaddle got stuck on a Deerling and got thrown over a cliff into a river with Ash diving in to save it. Arti then used his Hahakomori to save both Sewaddle and Ash from going over a waterfall. Sewaddle was very thankful to Ash and happily allowed him to capture it.
