Struggling pop princess Britney Spears will reprise her successful role as a receptionist in an upcoming episode of the TV series How I Met Your Mother, reports People. “The show is ecstatic and so is Britney,” said an insider. It's not clear if everyone will be quite so ga-ga. Neil Patrick Harris, who plays Barney, recently groused about "stunt casting" to boost ratings. (More Britney Spears stories.)