Swadloon, as a Sewaddle is Mio's second Pokémon she caught in the episode "Sewing With Mio!"
She was later used when Mio ask her to use its String Shot to shut up Ritsu's remarks, then Mio bonked Ritsu afterwards. She is easily defiant when talking to Sawako, after rejecting Sawako's request to make costumes for her.
As a Sewaddle, she does have a soft side for Mio, Mugi, Azusa, Ui and Yui, and is highly affectionate to Mio, she dreams about evolving all the way into a Leavanny.
In Sewaddle Cloaks Out!, she made its first battle debut against Izzy's Grotle but lost, despite the type advantage, however Team Rocket kidnapped Mio by accident after she shielded Sewaddle, seeing how brave Mio was, she evolved into Swadloon and learned GrassWhistle and Struggle Bug which sent Team Rocket blasting off.
In Mio's Forest Bond, As a Swadloon, She felt Mio's embarrassments due to a flashback, hearing the story about it, she was touched by Mio's story, but the bond was so strong that it made Swadloon evolve into Leavanny and learned Return, X-Scissor and Leaf Blade in the process.
As a Leavanny, she is really kind due to her species, she is often a fashion designer, and often helps Mio with Elizabass, she would often use her Grass Whistle, not for a sleeping move but for music. Her personality is really motherly and often concerned with others and Mio.
In "What's In a Nickname?", she was officially nicknamed Nana by Mio, and even nicknamed the other Pokemon she has.
Leavanny's known moves are: GrassWhistle, X-Scissor, Leaf Blade, Return, and her ability is Swarm. As a Swadloon, she had Leaf Guard.