Gengar

This is the third and final evolutionary stage for Gastly. Under the full moon, this Pokemon likes to mimic the shadows of people and laugh at their fright. In "The Tower of Terror," Ash, Misty, Brock and Team Rocket are teased and taunted by three over-the-top ghost Pokemon. Gengar finds that Jesse and James are especially fun to play with — so it keeps them tied up in the playroom while Ash and Haunter say their good-byes.

First appearance: Episode 23—"The Tower of Terror"