Kevork Djansezian / AP
Prince was a surprise performer on the 2006 finale of American Idol.
How it worked:
To promote last years album 3121, Prince stooped to performing on American Idol, which may be a highly entertaining karaoke show, but its still a karaoke show. Although it generated press and inspired debates about the use of American Idol as a marketing tool, chances are you still dont own 3121.