During the nail-biting conclusion of "American Idol" Season 21, viewers were treated to yet another unexpected development. During the three-hour event that aired live from coast to coast on ABC on Sunday, the final three candidates, Megan Danielle, Colin Stough, and Iam Tongi, each took the stage for the very last time in an effort to gain votes from viewers. As is customary, the judges Katy Perry, Luke Bryan, and Lionel Richie offered their comments and criticisms, but in this last round of the competition, all they could do was offer praise and best wishes to the contestants as they…