There's was a lot of celebrating at Kelly Clarkson's Wednesday night concert at Los Angeles' Staples Center.

In an emotional moment, the American Idol alum revealed that she is pregnant with her second child -- but her baby news didn't keep her from also celebrating Demi Lovato's 23rd birthday.

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Clarkson fans know she loves a cover, and in honor of the birthday girl, the 33-year-old singer performed Lovato's new hit, "Cool For the Summer."

"It's one of my girl's birthdays tomorrow...and when I say my 'girl,' I mean Demi Lovato," Clarkson said as the crowd cheered. "She's always been so supportive and so cool."

Clarkson has expressed her admiration for Lovato in the past.

"I love her. She's so sweet," she told MTV News in March. "Every time we see each other, she's always like, 'I like Kelly Clarkson,' she's always so nice, she's like my biggest fan and I love it. It's so awesome, we're both Texans."

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Lovato was blown away by the cover, and even admitted that she got choked up.

"WOW WOW WOW.. @kelly_clarkson thank you SO MUCH for covering #coolforthesummer at your show tonight!!!" Lovato tweeted. "BEST BDAY GIFT EVER!! *literal tears*"

Emotions were running high Wednesday night and not just for Lovato.

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"I was not planning on announcing this. I'm totally pregnant again," Kelly then admitted, while laughing. "That was not planned. I just didn't want you to think I was crazy. Honestly I'm just hormonal today. Nothing's wrong. I'm okay. I haven't vomited yet!"

See more of Clarkson's sweet, tearful pregnancy announcement:

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