Flashback to the show's first season: Clarkson delivered a tear-filled rendition of her very first single, "A Moment Like This," just after being crowned the inaugural Idol.
"It does seem like it's happened very quickly," American Idol host Ryan Seacrest told ET after the broadcast. "I look at her and I see her, and I think about standing on stage as we were talking tonight -- and I think about that first finale, it seems like it wasn't that long ago."
During Thursday's show, Clarkson joked that her pregnancy hormones were to blame for crying through her performance. But to hear Seacrest tell it, Clarkson's baby-on-the-way seemed to be fully enjoying all the action!
"She did say at one point that baby was kicking during a commercial break, and she began to rub her belly," he revealed. "So the baby was enjoying the show."
Among the most emotional audience members was none other than Idol judge Keith Urban, who openly wept from his seat at the table. "That song, it's sad! I figure you're either crying at this performance or you need to check your pulse," the father of two told ET.
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"I was starting to wonder if maybe I was [pregnant] too," he added with a laugh. "Tears were falling out. I'm like, 'Am I hormonal?! What's going on?'"
Meanwhile, Urban's fellow judge, Jennifer Lopez, can't help but feel sentimental over the impending end of an era.
"This is our top 10, our final top 10 of American Idol ever," she
told ET. "I think all the contestants feel the weight of what is
happening and with Kelly there as well, and her being emotional -- she
says she was pregnant, but I think everybody's emotional right now. It's
been such a beautiful journey."