In the Orange Archipelago, Ash and Tracey were paralyzed by a Vileplume's Stun Spore attack. Misty was left to fetch the cure, Salveyo weed, a special type of aquatic plant found at the bottom of lakes on which Poliwag feed. A friendly wild Poliwag helped her gather the special plant. Poliwag obviously liked Misty because it insisted on coming along with her, and Misty added it to her team.
In Johto, Ash and Misty both used Lure Balls on a wild Totodile. The balls captured the Pokémon out of sight, so Ash and Misty had a tournament to see who got the toothy Template:Type2. During a battle against Bulbasaur, Misty's Poliwag evolved into Poliwhirl. Although Misty still lost, she concluded that she preferred the Poliwhirl who was willing to evolve to help her to the Totodile that essentially did whatever it wanted.
Later, on the way to Blackthorn City, Misty fought a Trainer with a Poliwrath and lost. Misty started to consider evolving her own Poliwhirl. Misty took her Poliwhirl to the local Pokémon Center to be healed. On the way, Poliwhirl picked up the King's Rock that Ash had won in a tournament. Misty did not notice this, and simply gave Poliwhirl to Nurse Joy for treatment.
Shortly afterward, in a battle against Team Rocket, Misty recovered her Poliwhirl and let it out, surprised to see it evolve into Politoed before her eyes. Misty was thrilled with her newly-evolved Pokémon.
Misty's Politoed is very cheerful, enthusiastic, and eager to please. For a while, it took up cheerleading.