Mash

Mash (Japanese: ) is Ash and Misty's daughter.

Looks
Mash has blue hair and wears a rainbow-colored shirt, a blue overall-dress and red shoes.

Role in series
Mash's birth was the focus of the first episode of the third season.

The second episode of that season, "Say Hello to Mash" begins with Team Rocket capturing Mash. When Ash and Misty find out the next morning, they go outside to look for her. After fighting Team Rocket, they successfully get Mash back and show her to their friends. Unfortunately, Mash has developed a bratty and sexual behavior as a result of Team Rocket briefly raising her, much to the bewilderment of Ash and Misty (though the latter shrugs it off as "she's only a baby, she doesn't know better").

The fourth episode of that season explains the reason as to why Mash has blue hair (previously she had terracotta hair). While Ash and Misty were decorating what was to be Mash's bedroom, Mash falls into a pot of blue paint and her parents try to get it off. Later on, the paint somehow turns her hair blue.

In the sixth episode, Ash and Misty are fed up with the way Mash has been behaving and consider finding a way to age her up in an attempt to fix it. By the near end of the episode, they find Entei who manages to age her to a child of six years old, however this does very little if anything to remedy her behavior.

Mash once visited Bonnie in the eighteenth third season episode "Mash's Playdate with Bonnie" as suggested to Ash and Misty by Bonnie's older brother Clemont, much to the former's reluctancy. Their time together mostly consisted of being annoying to each other, which ended with Bonnie in a tearful state. With that, Ash and Misty then decide to no longer allow Mash to spent time with anyone else without their consent.

The thirty-ninth episode ends with Ash getting so fed up with Mash's behavior that he locks her into a crate and throws it into the ocean, before she emerges from the ocean and turns into a demon-like shark with red eyes.

The fortieth and last episode of the third season, "Mash the Demon Shark", involves Ash and his friends attempting to fight the now-shark Mash.

Trivia

 * Mash was actually based on a character from the first Japanese trailer for Pokémon: The First Movie which viewers interpreted as Ash and Misty's daughter, right down to the name.