Was "Friday" so popular because it's catchy or because it's the worst song ever? Either way, it's turned this 14-year-old into a household name. The clip, which Rebecca meant to be a serious music video, went viral when it was posted to the "Tosh.0" blog under the heading "Songwriting Isn't for Everyone" in March. But Rebecca has certainly reaped the rewards of Internet infamy: She starred in Katy Perry's "Last Friday Night (T.G.I.F.)" music video, and "Friday" has been covered by everyone from the "Glee" cast to Jimmy Fallon. Most recently, Kohl's used the song in its Black Friday commercial. It really is the song that never ends.