Idina Menzel Sings 'Let It Go' with Two Adorable Frozen Mini-Elsas During Book Signing

Idina Menzel is inspiring a whole new generation of Frozen fans.

At a signing for her new children's book, Loud Mouse, the 51-year-old Broadway star and voice of Elsa in Frozen, spontaneously shared a sweet moment singing "Let it Go" with two little girls dressed up as her popular Disney character.

In the video, Menzel can be seen encouraging the girls to join her in the front and when they do, she instructs them to "turn around [facing the audience] and sing with me."

As Menzel leads them into the chorus of the hit song, the two girls dressed as Elsa (along with an audience full of children and parents) join in singing the rest of the song. After the song ends, Menzel cheers and acknowledges the girls for their singing.

RELATED: Idina Menzel and Sister Cara Mentzel Write Book to Inspire Kids to 'Embrace' Their Inner 'Light'

Lanae Brody; Alberto E. Rodriguez/Getty for Disney

The Disenchanted star got candid about creating Loud Mouse, which was released in September, with her sister Cara Mentzel, saying that she wanted to create the book to help empower young readers to step out into the light and not be afraid of what other people think.

"That's something that I've dealt with ever since I was a little girl: wanting to step into my light, my spotlight to shine, to embrace this voice that I had, but also not wanting to alienate the people around me," said Menzel.

She explained that she didn't want to "seem like I was too much for anyone, that I was showing off, to bring attention to myself." But, that changed as she grew up and gained more knowledge.

"As I've grown older, I realize that we're doing a disservice to the world when we hide our talents and our gifts," Menzel said. "And when I finally understood that is when I finally found joy in what I was doing and acceptance. So, that was when I called Cara one night and said, 'Now go write a book about that.'"

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"I think the message we want us to send is that we have a job to shine in whatever way we can and not to shy away from that," Menzel's sister Cara said. "And that's not a selfish thing, that's not a conceited thing, that's what we're here to do."

Menzel said she also wanted to wait until they got the story and the message behind it right before publishing a book.

"Nothing against some of my peers, but I didn't want to do a celebrity-driven kids' book for the sake of doing it," she says. "I wanted it to come from a real place, and I wasn't sure what that was yet."

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But she said having her sister — a former elementary school teacher — there to help her visualize and create the story for children helped.

"I knew that she would help me interpret whatever it was that I wanted to do because she knows me," said the actress. "She's a great writer, but also a teacher of kids this age. [Cara] has an understanding of children's literature from a literacy standpoint, from a content standpoint— she's a good artist, everything."