Demi Lovato received a very special 23rd birthday surprise last night, courtesy of Kelly Clarkson (and no, it's not the news that the "Stronger" singer is expecting her second child). 

The American Idol winner, who hasn't met a cover she can't slay, covered Lovato's hit "Cool For the Summer" last night during Los Angeles concert at Staples Center, and as expected, she totally killed it. 

"It's one of my girl's birthdays tomorrow...and when I say my 'girl,' I mean Demi Lovato," Clarkson told the audience. "She's always been so supportive and so cool...I thought I would, for her birthday, sing her new single." 

After the concert, Lovato quickly caught wind of the b-day treat and tweeted her appreciation to the "Since You've Been Gone" beauty. 

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Demi Lovato, Kelly Clarkson

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"WOW WOW WOW.. @kelly_clarkson thank you SO MUCH for covering #coolforthesummer at your show tonight!!! BEST BDAY GIFT EVER!! *literal tears*" the former Disney star wrote last night, adding, "23 is gonna be AMAZING!!!! I'm already crying from joy!!!"

This isn't the first time Clarkson has sung Demi's praises. In fact, she told MTV News in March that the two had plans to collaborate but the project fell through. 

"We almost got to work together, but I was pregnant and she had asked me to sing, I totally was down, but it just didn't work out," she said. "She was touring, I was super pregnant and not feeling well and it didn't work out this time, but it totally will. … I love her; she's so sweet. Every time we see each other, she's always like, 'Kelly Clarkson, she's so nice, and so awesome, we're both Texans.'"

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Kelly Clarkson, Demi Lovato

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Of course, that wasn't the only surprise Clarkson had up her sleeve at last night's show as she also made an impromptu pregnancy announcement.

"This is not how I wanted to announce [that I'm pregnant]. My makeup artist is backstage hating me. I didn't want you to think I'm on pills or something," she told the crowd, adding "I would like to apologize to my husband. This was not planned. I'm just so hormonal. Everything is great, I haven't vomited yet. That's a win y'all."

Clarkson tied the knot with Brandon Blackstock in a romantic ceremony in front of close friends and family in 2013. The two are also parents to 1-year-old daughter River Rose Blackstock

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