Kelly Clarkson was a guest judge in Episodes 1509 and 1510 during the Quarterfinals of America's Got Talent Season 15. She took Simon Cowell's place on the judging panel while Cowell was recovering from a back injury. 
Kelly Brianne Clarkson (born April 24, 1982) is an American singer-songwriter, actress, author and television personality. She rose to fame in 2002 after winning the first season of American Idol, which earned her a record deal with RCA Records. Clarkson's debut single, "A Moment Like This", topped the US Billboard Hot 100 chart and became the country's best-selling single of 2002. It was followed by the release of her debut studio album, Thankful (2003), which debuted atop the US Billboard 200. Trying to reinvent her image, Clarkson parted ways with Idol management and shifted to pop-rock music for her second album, Breakaway (2004). After numerous top 40 radio number-one singles, such as "Since U Been Gone" and "Because of You", the album sold over 12 million copies worldwide and earned Clarkson two Grammy Awards.
She has been a coach on the US version of The Voice since Season 14, and she has accumulated 3 wins as of 2020 (including a victory in her debut season). 
In 2020. she won the Daytime Emmy for Outstanding Entertainment Talk Show Host for her work on her syndicated talk show, The Kelly Clarkson Show.
- Kelly is the third person to be a guest judge in the live shows, behind Sean Hayes and Queen Latifah.
- She is the first guest judge to fill in for a regular judge during the live shows.
- She is the first person to go from a guest performer to a guest judge.