Timmy appeared as a character of the day in The Purr-Fect Hero (EP053).
When Ash and friends showed up at Timmy's school for Kids Day, he was the only kid who wasn't interested in playing with their Pokémon. He only wanted to interact with Meowth—specifically, because a Meowth had once saved him from a Beedrill.
Team Rocket ended up kidnapping him, and Timmy became convinced that their Meowth was the same one who'd rescued him years before. Jessie and James saw an opportunity and forced their Meowth to pretend to be Timmy's friend. The scheme fell apart when Meowth actually spoke in front of Ash and the others, giving them away. This led to a confrontation between Team Rocket and Ash, which got cut short when a rockslide erupted. A massive boulder came down on both Timmy and Ash—but the real Meowth showed up and saved them both, just like before.
Timmy decided to keep the Meowth and told Ash he planned to enter the Pokémon League with it once he was older.
Content compiled by AnimeList.moe from publicly available sources.
