Misty's first appearance was in the very first episode of the anime series, Pokémon - I Choose You! In this episode, she first meets Ash after fishing him out of the water when he was trying to get away from Spearow. Ash then takes Misty's bike from her in order to escape the Spearow, which is then wrecked by Pikachu's Thunder Shock. Misty then tracks down Ash and follows him around on his adventures until he can pay her back. She eventually forgets about the bike and becomes one of Ash's ex closest friends. She is currently the Cerulean City Gym Leader.
Misty has a slight inferiority complex, mostly due to her three older sisters Daisy (oldest), Violet (second-from-oldest) and Lily (third-from-oldest), who formed the group, "The Three Sensational Sisters" (their synchronized swimming group), and refer to Misty as the "runt"or "weaker one". This complex diminishes over time as Misty grows closer to Daisy. Until Misty became the Cerulean City Gym Leader, her three older sisters were the ones who ran the gym, although when Ash came along to get his Cascade Badge, it was Misty who battled him for it.
Despite being the youngest of four sisters, Misty's the smartest and the most mature and responsible of her sisters, with Violet being the next smartest and next most mature and responsible. Even if Misty's sisters can be kind of mean to her, they really do care about her, they just aren't very good at showing it sometimes.
Misty specializes mainly in Water-type Pokémon, which are her favorite type, but she's had other types, and she also deeply admires Lorelei, an Ice-type Pokemon trainer. Misty aims to become a world-class trainer, and her well-trained Pokémon reflect her aspirations of becoming a top trainer. Her least favorite type of Pokemon are Bug-type Pokémon, as she has a deep-rooted fear of them. However, Misty's fear lessens over the course of the series, but not to the point where she's totally gotten over it, as shown in A Real Cleffa Hanger.
As the series continues, she gradually shows herself to be kind and sensible. She restrains Brock from girls, often pulling him away by the ear.
In the series, Misty first is seen wearing a yellow tank top with red suspenders and light blue denim shorts. Her shoes were colored red and white, with a yellow streak in the middle. Misty's personality in the anime can be very complex at times. She can be very nice to her friends but will then quickly change moods in a short amount of time, particularly anger. She is quite proficient in anything having to do with water as can be seen in certain episodes where she has ability in fishing, swimming, and overall Water Pokémon training. Even though she wanted to stay with Ash, Misty felt obligated to watch over the Gym. The two went their separate ways, and Misty became the official Gym Leader at Cerulean City's Gym.
Misty's second costume is later shown after she meets up with the main group in Hoenn, after she had already left. Here she wears a yellow, sleeveless jacket with a blue collar, and a large blue button. She also wears short, form-fitting shorts that is connected to a crimson colored upper body piece, which may be a swimsuit. Her shoes are now light and burnt orange.
Misty has only appeared as a guest star in the remainder of the Pokémon series. In one of her cameo appearances in the Advanced Generation series, her Togepievolves into Togetic. Misty releases Togetic after it chooses to stay behind to defend the Mirage Kingdom. After Ash finishes competing in the Hoenn League, he returns home to Pallet Town to find Misty waiting for him. However, she isn't the only one to rejoin Ash, as May, Max, and Brock join him as well for the Battle Frontier challenges. She travels with Ash for two episodes, and shortly after returns to her Gym.
Pokémon the Series: XY
She appears return in the future episode of Pokémon the Series: XY when Misty dies?.
Gyarados and Misty have a nice relationship at Cerulean Blues. When she appeared in Pokémon Advance Ash,everybody else was shocked of how she was controlling a Gyarados and she got over her fear of it.
Misty's Politoed is one of Misty's Pokémon that she caught in the Orange Islands as a Poliwag. It evolve from Poliwag to poliwhirl in "The Totodile Duel" and evolved again from Poliwhirl to Politoed in "Outrageous Fortunes" when it accidentally touched a King's Rock, causing it to evolve. It currently resides in the Cerulean Gym with Misty.