Mariah Carey left the cast of "Schitt's Creek" tongue-tied after she surprised the actors during YouTube's Dear Class of 2020 graduation special.

Eugene Levy, Catherine O'Hara, Daniel Levy and Annie Murphy – playing their beloved characters Johnny, Moira, David and Alexis Rose – came together virtually to sing Carey's iconic song "Hero" in honor of all the teachers and students who have prevailed during the pandemic.

Then, the Grammy winner jumped in, a fan blowing her hair and all.

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"Moira, darling, I hope you didn't mind that I jumped in like that," Carey said as the other characters gasped. "You all sounded so good that I had to get in on it."

Daniel, as David, yelled, "I think I'm having a heart attack!"

Carey also sent her own message to the graduates, "To the students who had to deal with this bleak moment, congratulations on this historic accomplishment,” she said. "To all the students and teachers, you are so appreciated. And I just want to say, Class of 2020, you made it!"

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The other cast members who sang along included Twyla (Sarah Levy), Ronnie (Karen Robinson), David's husband Patrick (Noah Reid), Stevie (Emily Hampshire), Jocelyn (Jenn Robertson) and Ray (Rizwan Manji).

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The YouTube Originals special also featured performances by Lizzo and her flute and Megan Thee Stallion, while Taylor Swift, Lady Gaga and Beyoncé gave inspiring speeches.

Former president Barack Obama and first lady and Michelle Obama participated as well and offered words of encouragement.

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The president said that the pandemic “brought into focus problems that have been growing for a very long time" while the "Becoming" author said, “what you’re going through right now can be your wake-up call.”