From Bulbapedia, the community-driven Pokémon encyclopedia.
Tiffany (Japanese: アサギ Asagi) is a character of the day who appeared in On Olden Pond. She lives in Kanto by a popular fishing lake, and she owns a boathouse along with her grandmother, Galea.
For over a year, a Crawdaunt appeared in the lake and frightened the Pokémon and fishermen away, wrecking Tiffany's livelihood. With the help of Ash, his friends, she discovered that the troublesome Crawdaunt belonged to Mr. Saridakis, a developer who hoped to turn the lake into Leisure Land, an amusement park and spa complex. Saridakis later abandoned his plans, mich to Tiffany's relief, after a wild Dragonair rescued him from drowning. The lake was soon restored to its crystal blue state by Dragonair and all of the Pokémon came back, allowing for it to thrive once more.