As soon as Ash and friends arrive on Mandarin Island and notice that all the Pokémon hate their trainers. Pikachu and Togepi falls under the dark spell as well, turning against Ash and Misty. Team Rocket arrive too and Meowth runs away. They soon realize it was the work of Team Rocket II (Cassidy, Butch and their new Drowzee). Can Ash break Drowzee's spell?
Cassidy and Butch made a reference to IL057: The Breeding Center Secret about how they acquired their Drowzee.
Although Officer Jenny's Ghastly is a ghost Pokémon she could still hold it as if it was an object you can touch.
The "Who's that Pokémon?" in this episode is Kangaskhan.