The Northern Lights Rooftop Party is introduced in the episode "Power Animal." This is the episode's first scene where Finn and Jake climb up to their rooftop for the party. When they're at the top, Finn does a backflip to amuse his guests, and Cinnamon Bun compliments him by saying he always focuses. Jake asks Cinnamon Bun if he focuses. Cinnamon Bun replies, "Jake, you don't focus at all," but Jake isn't listening because he is trying to toast some ice cream.
Afterward, a hefty gnome approaches Finn. Finn asks Jake who the gnome is, referring to him as "super weird," but Jake replies that he thought the gnome was his friend. Their attention is directed elsewhere when Princess Bubblegum announces that the "celestial alignment" (aurora) is starting.