The Grim Adventures of Billy & Mandy.
It's the annual Citrus Festival at school and they are hosting a Citrus Fest talent show. Mindy has all intention of winning the talent show and being crowned "Citrus Queen." However, after taunting Mandy about it, she decides to join in the talent show.
Mandy agrees to participate in the talent show but in order to do so, she must smile. As long as her friend Billy has known her, she has remained a "stone-faced deadpan snarker", and he, along with Grim, decide to assist Mandy with her smile. Eventually, Grim calls an old friend of his, Crabina, the best makeup artist in the Underworld. She gives some acting tips and applies some makeup to Mandy (who is still a bit reluctant).
After a couple of acts, it's Mandy's turn. She sings "Over the Rainbow." During the act, everybody cheers her on, even more then they cheered on Mindy. But, it comes to the end of the act, where Mandy must smile. She finishes her song, and she smiles. Suddenly, the entire world randomly implodes, and Billy, Mandy, Grim and Irwin are sent to the city of Townsville, the setting of the Powerpuff Girls.
- The episode features cameo appearances from Professor Utonium from the "Powerpuff Girls", another Cartoon Network series.
- Mandy has actually smiled in other episodes before this episode, such as Meet the Reaper. It didn't have any dire consequences. (Response: Those were all Grim & Evil episodes and early first season Grim Adventures episodes so the writers did not create the effect yet).
- There was a reference to Stanley Kubrick's film 2001: A Space Odyssey when the world imploded, an eerie array of colors and horrfied faces resemble the climax from the film.
- Mandy is dressed up like Dorothy Gale and sings Over the Rainbow, a song from the 1939 movie classic The Wizard of Oz, starring Judy Garland.