The show’s final episode

Series executive producer Nigel Lythgoe promised the finale would celebrate its large ranks of contestants, and he stuck to that pledge.

The show opened with a harmonizing chorus of white-clad winners and contenders including Scotty McCreery, Taylor Hicks and Diana DeGarmo.

Other familiar faces popped up in solos and group numbers, including Carrie Underwood, Jennifer Hudson, David Cook, Fantasia, Ruben Studdard, Jordin Sparks and Kimberley Locke.

Judges got in on the act as well. Keith Urban and Underwood duetted, while Harry Connick Jr. saluted a music center in New Orleans’ Katrina battered-Ninth Ward by inviting a young student, Marley Fletcher, to join him on “It’s a Wonderful World.” Jennifer Lopez performed her new single.

Clarkson, who’s expecting her second child soon, appeared in a pretaped performance.

There was a brief nod to nostalgia, with clips from past auditions presided over by original judges Simon Cowell, Paula Abdul and Randy Jackson.

“American Idol” debuted in June 2002. No other TV talent show has achieved the same track record of fame for contestants.

“Idol,” which averaged more than 30 million weekly viewers at its 2006 peak and ranked No. 1 for nine consecutive years, averaged about 11 million last season.