The Trap Door Sezon 1 Odcinek 5: Gourmet's Delight

Berk is cooking again, when something invisible comes out of the trap door and starts throwing things about. Berk scores a direct hit in retaliation with some yellow goo and the little creature, Bubo becomes visible and bright yellow. When Berk eventually catches the naughty Bubo, he finds a hole in the top of his head, blows him up like a balloon and lets him off into the air and lets him drop back down the trap door.