Meet Fox's "American Idol XV" Finalists - Arrivals"American Idol" is going out with a three-night spectacular when it wraps its 15th -- and last -- season next month, and the show will welcome back its two most famous former contestants to mark the milestone.

Both Kelly Clarkson, the inaugural "Idol" champ, and Carrie Underwood, who claimed the season four crown, will return to the show on April 7, where each will perform on the final night of "Idol"'s three farewell episodes. The appearance will mark the second time Clarkson has performed this season, after she sang an emotional rendition of her single"Piece by Piece" on the show back in February.

In addition to those two nostalgia-inducing guests, "Idol" is pulling out all the stops for its final bow with what's it's dubbed Grand Finale Week, beginning on April 5 with a 90-minute retrospective called "American Idol: American Dream." The show will feature host Ryan Seacrest along with multiple past winners and former contestants, current and former judges (fingers crossed that Simon Cowell is among them), and members of the "Idol" crew, who will share behind-the-scenes memories.

On April 6, the final performance episode of the show will air, featuring the last two contestants standing this season, who'll duke it out for the audience's votes. The season 15 winner will be crowned the following night, alongside performances from Clarkson and Underwood and other special, TBA guests.

The farewell tour begins on Tuesday, April 5 at 8 p.m. with "American Idol: American Dream," continues Wednesday, April 6 at 8 p.m., and concludes on Thursday, April 7 at 8 p.m., all on Fox.

[via: Deadline]

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