Episode #23 - The Tower of Terror
Ash went inside the Pokemon Tower in Lavender Town and met three ghost Pokemon: Gastly, Haunter, and Gengar. They were trying their best to act funny, but Ash wasn't so entertained. They were very sad, and left. Ash temporarily became a ghost too because a light crashed on him, and flew all over the city with the three Pokemon. They all really had fun. But now it's time for Ash to leave, because his dreams were to become a Pokemon master. The ghost Pokemon were very sad. In the end, Haunter went with Ash to Saffron City, and scared the life out of Brock and Misty.