The end credits feature pictures of those who are banned for life from the water park. They feature, in order: Donny, Magic Man, Squirrel, Tiffany, Lumpy Space Princess, Lemongrab, Ricardio, and Ice King.
This was a miscalculation from the outset. The guest animator/writer/director David Ferguson significantly misjudged the style of the show. Rather like David Cronenberg writing and directing an episode of Friends: you know that it can't work. And it doesn't here. It's also just a boring episode that adds nothing to the overall story or world of Adventure Time.