Best: Prince Makes a Surprise Appearance, Season 5
American Idol was riding sky-high during Season 5, raking in some of its biggest ratings ever. In fact, the 2006 finale drew almost 40 million viewers. Also experiencing immense success that year? Prince, whose album 3121 was his first to ever debut at Number One on The Billboard 200. So, perhaps it's no wonder the two decided to team up. His Royal Highness reportedly breezed in mere minutes before walking onstage to perform two songs off the album — "Lolita" and "Satisfied" — and then breezed right out. And that, folks, is how an old pro (especially one named Prince) does it.