Kelly Clarkson and Carrie Underwood, as well as some other well-known country names, have signed on to appear during the grand finale episode of American Idol.

Clarkson and Underwood, both of whom got their start on the singing competition show, will make appearances during Idol's two-night series finale, scheduled for April 6 and 7. Additionally, country stars and former Idol contestants Scotty McCreery, Bucky Covington, Casey James, Josh Gracin, Kellie Pickler and Lauren Alaina will stop by, as well as a host of other former competitors from throughout the show's 15 seasons.

Clarkson, who is pregnant with her second child, pre-taped her appearance earlier during this American Idol season, when she stopped by the set for an emotional rendition of her song "Piece By Piece." The performance struck a cord with judge Keith Urban -- and pretty much everyone watching -- who cried while Clarkson was onstage.

“We were rehearsing that day, and I just couldn’t get through it. My 1-year-old is running around the same hallway as I was at 19,” Clarkson recalls about the performance. “... [My husband, Brandon Blackstock] was there, my little girl was there, my little boy was, like, turning circles in my stomach. It was nostalgic. It was the last time I was going to be on Idol, and it’s ending. I was screwed from the get-go.”

Prior to Idol's grand finale, Urban -- who serves as a judge on the show -- is set to perform, during the singing competition's March 31 episode. He has not yet revealed what song he'll be performing.

American Idol's Country Contestants: Where Are They Now?

Unforgettable American Idol Auditions