She is a Water Pokemon Master.
A stubborn tomboy, Misty is the youngest of four sisters who live in the Cerulean Gym. Fed up with her more glamorous older sisters, Misty left the Gym with the goal of becoming the world's greatest Water Pokémon Trainer. She first met Ash when she "caught" him with her fishing line in a river between Pallet Town and Viridian City. She traveled around with Ash, Brock, and Tracey through the Kanto region, the Orange Archipelago, and the Johto region.
Her purpose was ostensibly to get Ash to replace her bicycle, which he had accidentally destroyed when they first met. However, Misty often seemed to have forgotten about the bicycle, indicating that her real reason for following along was that she simply wanted to remain with her friends. During her travels with Ash, she, aside from training to become the best Water Pokémon Trainer, also acted as his coach in many Pokémon battles. It was also her job to drag Brock away from women by his ear.
Misty made her anime debut in Pokémon, I Choose You!, fishing in a nearby river on Route 1. As her fishing rod snagged something, she managed to pull out not a Water-type Pokémon, but Ash and his injured Pikachu, who were being chased by a flock of Spearow. After pointing Ash in the direction of the nearest Pokémon Center, the one in Viridian City, he borrowed her bike, saying that he would return it someday.
In the next episode, Misty appeared in the Pokémon Center after Ash dropped off his Pikachu, holding her charred bike and demanding a new one right away. She got distracted from her demands when Nurse Joy brought Pikachu out, sad to see Pikachu in such condition. Before anything else could be said, an Ekans and Koffing burst through the ceiling, and Team Rocket come through as well. After helping Nurse Joy and Ash wheel Pikachu into the back room, she told Ash to help defend the Pokémon Center with the Pokémon in stock. After a few failed tries, she decided to step in herself, and sent out her Goldeen to buy some time, though she quickly recalled it since it couldn't battle on land. Later in the episode, it was revealed by Officer Jenny and Nurse Joy that Misty had gone with Ash to the Viridian Forest. As the screen cuts to them, Misty lets out a scream, seeing a Bug-type Pokémon, which happens to be a Caterpie, revealing her fear of Bug Pokémon. She told Ash to do something about it, so he decided to throw a Poké Ball at it.
Misty participated in the Whirl Cup alongside Ash from Octillery the Outcast to The Perfect Match!. She defeated Ash in the second round and made it to the best eight of the competition before she narrowly lost to Trinity.
After Ash competed in the Silver Conference, however, her bicycle was repaired and returned to her by the Viridian City Nurse Joy. Misty was shown to be sad that she no longer had the convenient excuse to travel with Ash, especially when she saw that Ash hadn't learned that and had assumed she followed him because of her bike. In addition, her sisters Daisy, Lily, and Violet, called Misty at this time to tell her they were going on a world tour, and needed her to return to Cerulean and watch the Gym in their absence. However, Misty saw how Ash truly cared for her when he saved her from a trio of Pokémon gangsters. Misty wanted to stay with Ash, but felt it was her responsibility to take over the Gym, which would be shut down if left unattended.
Upon the return of her sisters, Misty remained the sole Cerulean Gym Leader. Since their return, only Daisy appears to spend any significant amount of time at the Gym. While working in the Gym, Misty sometimes receives help from Tracey when he is either visiting or running an errand for Professor Oak.
Failed to Catch Pokemon