El Dia de Los Muertos Estupidos / Heartburn When Billy's dad drives Billy, Mandy and Grim to the hamburger restaurant, they somehow end up in Mexico. There, the people are celebrating Dia de los Muertos, but local kids say it may be the last celebration ever, because Del Uglio, a masked and ugly luchador, is set on stealing the "Golden Nose of Chipotle", a prehispanic relic on which the festivity is based. To get to the nose, Del Uglio has one half of the map, while the other half is held by his lost twin brother, who turns out to be Billy. Grim defeats Del Uglio, but it is Mandy who keeps the golden nose for herself, which makes her rich. When Billy starts taking pictures with a camera found in Grim's trunk, Grim tells him that is an Underworld's True-heart Camera, which shows the real essence of a person's heart. When Mandy takes Irwin's picture, it is revealed that he is actually half-good and half-evil. Irwin explains that although he was born evil, his dad taught him about love and respect, and he had a change of heart. Upon knowing this, and against her own wishes, Mandy also experiences a painful change, turning good and kind-hearted. Mandy and Irwin finally share a romantic kiss in this episode, but it makes Mandy revert to her old dark and sinister self, which was Irwin's true intention, as he likes her just the way she is.