Adam Lambert made his return to American Idol on Thursday, debuting his new single, "Welcome to the Show," and performing one of the most famous covers from his run on season eight of the singing competition show. Lambert opened up to ET afterward about performing on the Idol stage once again.
"It's nostalgic. I've been back on the show every year since I've been off, and so each year it's something different," he said. "It's really nice to come back for the final year with a new single and to reprise 'Mad World,' which was really cool."
Lambert also opened up about Kesha, whom he recently spent time with in Nashville, Tennessee, where the embattled singer accepted the Visibility Award at the 21st Annual Human Rights Campaign Nashville Equality Dinner earlier this month.
"From what I know, she's doing really well," Lambert said. "We go way back from when we first both got signed so it was really nice to see her."
Lambert's not the only former Idol fave to return to the singing competition this year. Kelly Clarkson brought the house down in February with an emotional performance of her single "Piece by Piece," which brought even the judges to tears.
EXCLUSIVE: Adam Lambert opens up about Kesha's legal battle, returning to the 'American Idol' stage
Adam Lambert arrives at the iHeartRadio Music Awards at The Shrine Auditorium on Sunday, March 29, 2015, in Los Angeles. (Photo by John Salangsang/Invision/AP)
Adam Lambert, left, and Brian May of Queen + Adam Lambert perform at Madison Square Garden on Thursday, July 17, 2014 in New York. (Photo by Greg Allen/Invision/AP)
Adam Lambert and Roger Taylor of Queen + Adam Lambert perform during the tour opener at the United Center on Thursday, June 19, 2014 in Chicago. (Photo by Barry Brecheisen/Invision/AP)
Adam Lambert arrives at the iHeartRadio Music Awards at the Shrine Auditorium on Thursday, May 1, 2014, in Los Angeles. (Photo by Jordan Strauss/Invision/AP)
NEW YORK, MARCH 6: Adam Lambert at Good Morning America to announce Queen touring this summer with Adam Lambert on March 6, 2014 in New York City. Credit: RW/MediaPunch
Adam Lambert arrives at VH1 Divas on Sunday, Dec. 16, 2012, at the Shrine Auditorium in Los Angeles. (Photo by Jordan Strauss/Invision/AP)
In this Friday Sept. 24, 2010 photo, US singer Adam Lambert performs on stage, in Singapore as part of entertainment events organized on the sidelines of the Singapore Formula One Race weekend in the city-state. (AP Photo/Joan Leong)
Adam Lambert performs at The 4th Annual Gridlock New Yearâs Eve Bash on Thursday December 31, 2009, at the Paramount Pictures Studio in Los Angeles. (AP Photo/Katy Winn)
Adam Lambert is silhouetted against dry ice as he rehearses for his performance in Sunday's 2009 American Music Awards, Thursday, Nov. 19, 2009, at Nokia Theater in Los Angeles. (AP Photo/Chris Pizzello)
Singer Adam Lambert performs on CBS News' "The Early Show" in New York, Wednesday, November 25, 2009. (AP Photo/Charles Sykes)
Adam Lambert, left, and Paul Stanley, of KISS, perform during the season finale of American Idol on Wednesday May 20, 2009, in Los Angeles. (Evans Vestal Ward/AP Images for Fox)
Singer Adam Lambert arrives at the Hollywood Life 11th Annual Young Hollywood Awards in Santa Monica, Calif. on Sunday, June 7, 2009. (AP Photo/Dan Steinberg)
Adam Lambert of Los Angeles, a finalist on "American Idol," arrives at the American Idol Top 13 Party in Los Angeles, Thursday, March 5, 2009. (AP Photo/Chris Pizzello)
American Idol finalists Adam Lambert, left, and Kris Allen are seen during the season finale of American Idol on Wednesday May 20, 2009, in Los Angeles. (Evans Vestal Ward/AP Images for Fox)
American Idol contestant Adam Lambert, of Los Angeles, talks with fans while the show was at Hitsville USA's famed Studio A to film a segment in Detroit, Thursday, March 19, 2009. The contestants were mentored by a pair of Motown legends, founder Berry Gordy Jr. and singer Smokey Robinson while they worked on Motown classics. (AP Photo/Paul Sancya)
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"I was really touched by her performance," Lambert gushed. "It was so honest, and I think that's what hit everybody in the heart. She's such a talented singer."
"As a fan of the show, I watched it from the beginning, before auditioning," he added. "Kelly's in all of our hearts. She's an incredible artist."