Idina Menzel on her new kid's book and the advice she gave Cynthia Erivo for playing Elphaba in the Wicked film

Every parent who has had their kid belt "Let It Go" knows that Frozen anthem is about finding your voice and being true to yourself. So it makes sense that those are the major themes of Idina Menzel's new children's book, Loud Mouse (out today) written with her sister, the writer and educator Cara Mentzel (who uses the original spelling of their family's last name).

The iconic voice behind Frozen's Queen Elsa and one of the stars of the upcoming Disenchanted had been approached about writing a kid's book many times over the years but she wanted to wait until she had the right idea. "The inspiration for it came from our childhood and my own complicated feelings I had as a little girl with a big voice, not quite sure how the world would perceive me if I was to really step into my own spotlight, and own this big, powerful voice that I had," says Menzel, 51, during a recent Zoom interview with her sister.

And that idea carries over to the advice Idina gave Cynthia Erivo, who is about to tackle Elphaba in Jon M. Chu's film adaptation of Wicked, a role that Idina won a Tony Award for in 2004. "I've congratulated her and she sort of asked me just to be a part of it and be there. And I offered to be in her ear if she wants me to and to give her a space because she doesn't need my help to be quite honest. But just always keep in mind what the whole story was about. Similar to our book is just like not being afraid of what makes you beautiful and powerful. And if you stay true to that, then you'll be true to Elphaba."

Theme aside, Cara says the making of the book was very mindful process: "I know that Dee" — her nickname for Idina — didn't want to just write a children's book for the sake of writing a children's book. It had to be something that was the right story for her to tell specifically. So when she came to me with that idea, it was my task then to figure out how best to communicate that to kids."

Loud Mouse is about the story of rodent sisters Dee and Cara Lee. Dee loves to sing and has a beautiful voice but she's not sure she likes how much space she takes up when she embraces her voice at full power. It's only with the encouragement of her little sister that Dee learns that "your best self is big, brave, and loud," as she says in the book, adorably illustrated by Jaclyn Sinquett. Idina also wrote a song to accompany the book which fans can listen to and download here.

After collaborating on the 2017 memoir Voice Lessons: A Sisters Story, writing a kid's book together was a natural fit for the siblings. "My sister knew me better than anyone so she'd bring a perspective and a way of communicating the book in a way that would be really appropriate for children," Idina says. They brainstormed the story together and Cara wrote the first draft. "With Cara, I just felt like my idea blossomed," Idina says. "Her first draft was just beautiful and it just brought me to tears because I think she's just such a great writer."

Cara used her knowledge as an educator to balance teaching and entertainment in the book. "I think it was at the forefront the whole time, because there were times where I was thinking about what word do I choose? I would go with the word that a kid might recognize on a page as opposed to a larger word that only the person reading it to them might know." Still, the creativity piece is just so fun — you're like, well, what would make them laugh?"

The two have already written a sequel called Proud Mouse, which focuses on Cara Lee's character. Idina says, "It's wonderful when the children teach the lesson in the book, as opposed to a parent coming in, having the answers. So I love that the wise soul is actually the Cara Lee character, who's the one there to say, 'Do your thing.'"

As to what kids and parents take away from the Loud Mouse, "we want kids to be their biggest, best selves" in Cara's words. Adds Idina: " I think you're doing a disservice to the world when you withhold your gifts and that being your greatest, biggest shiniest self is what you're meant to do."

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