The big surprise guest performer during the American Idol finale tomorrow night will be "Freedom" hit-maker George Michael, a source has exclusively revealed.

Earlier this week, producer Nigel Lythgoe refused to reveal who the artist would be, only saying that the "biggest star in the world" was coming to Idol.

The appearance will time in nicely for the former Wham! frontman, who starts a 20-city tour on June 17 in San Diego in support of his recently released...