Murphy persuaded the Fleetwood Mac icon to appear as herself in the Jan. 8 episode — and yes, there will be singing. ''It's part of Fiona's ruse, in that Fiona is trying to get the true Supreme to reveal herself because she needs to stay alive. So she tells Misty Day [Lily Rabe] that the Supreme gets so many great things like tickets to the Oscars and the Met Ball. So she brings Stevie Nicks in as a gift to Misty to prove to her that if she exhibits more power, she'll get that and more. Then the other girls come home and see Stevie and Misty singing, and it starts them trying to move much quicker to prove that they are the Supreme.''