Casey (Japanese: ナナコNanako) is a trainer from Johto. She is shown to be confident and cheerful. She is a fan of the Electabuzz Baseball team. Once, in a flashback, it showed that Casey's entire family are fans of the Electabuzz Baseball team.
During the Bug Catching Contest, Ash caught a Beedrill that Team Rocket tried to steal. Casey saved Ash and evolved her Chikorita. During the end, Ash won the contest along with Beedrill and a Sun Stone. Ash gave Casey that Beedrill because Casey loved Pokémon that are yellow with stripes.
Ash spotted a wild Elekid which bullied Larvitar. Soon, Team Rocket stole both of them and thats when Casey came telling Ash about her find of Elekid. Ash told her it was stolen by Team Rocket and they searched. Larvitar and Elekid escaped and they befriended. At the end, with the help of Casey's Meganium, Casey caught the Elekid after a launch of Solarbeam.
In the episode "A Date With Delcatty", Casey loses in battle with Georgio (The winner of the battle would get tickets to an Electabuzz baseball game). The two of them end up going to the Electabuzz game together at the end of the episode.
Casey appears in two episodes of Pokémon Chronicles, and is shown to wear a cheerleader outfit.