Clarissa Wellington

From the animated TV show The Simpsons (05/08/2005).

In the "A Star is Torn" episode, Lisa Simpson (voiced by Yeardley Smith) enters the Krusty the Klown Li'l Starmaker Competition, a preteen American Idol spoof. The first round puts her up against much better singer Clarissa Wellington (voiced by real Idol Fantasia Barrino), who sings the same song Lisa planned to sing ("Mockingbird"). Dad Homer Simpson saves the day by quickly writing Lisa a pro-Springfield song that panders to the crowd (having previous songwriting experience with his barbershop group The Be Sharps).