Biennial Gumball Ball

The Biennial Gumball Ball is an event held in the Candy Kingdom by Prince Gumball. Gumball asks Fionna to go to it with him, as his "pal." Jelly Kinders are used as decorations for the event. Later on in "Adventure Time with Fionna & Cake," many gender-swapped Candy People, Marshall Lee, and Lumpy Space Prince are seen during the event.

Because this event is only mentioned in the Ice King's fan fiction, it's unknown whether it exists in the real Land of Ooo.