The film is inspired by How I Met Your Mother co-creator Craig Thomas' son Elliot
Kristen Bell and Jonathan Groff
Kristen Bell (L); Jonathan Groff
| Credit: Bennett Raglin/Getty; Roy Rochlin/FilmMagic

Anna and Kristoff are back — but not in the way one might expect.

Frozen stars Kristen Bell and Jonathan Groff are reuniting on the big screen for a new musical called Molly and the Moon, written and directed by How I Met Your Mother co-creators Craig Thomas and Carter Bays.

Molly and the Moon tells the story of Kate (Bell) and Brian (Groff), a couple expecting a baby girl, whom they sing to while she is still in utero to help her find her way to the moon — a metaphor for "being alive and participating in the world," Bays, 45, told Deadline.

The story was inspired by Thomas and his wife's experience with their son Elliot. "We discovered after he was born that Elliot had Jacobsen Syndrome, a rare genetic deletion where a piece of one of the 11th chromosomes has broken off, resulting in the loss of certain genes that go into making a healthy, typical baby," Thomas said, explaining that he and his wife were not initially able to hold their baby.

"What do you do when you can't hold your baby? You sing to your baby," Thomas continued. "Singing was our way of speaking to Elliot."

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Kristen Bell
Kristen Bell at Frozen 2 premiere
| Credit: Amy Sussman/Getty Images
Jonathan Groff
Jonathan Groff at the Frozen 2 premiere
| Credit: Kevin Winter/Getty Images

"That is the reason we made Molly and the Moon a musical, and to this day, music is such a part of what defines Elliot. It got him to stand up, and he walked and talked because of music," he added of his son.

Thomas went on to share that his wife "made up a little simple lullaby about [Elliot's] name that she would sing to him that just sort of came to her there in the [neonatal intensive care unit], and that actual melody and lullaby is what we use in the movie. The meter of Molly Moon is sort of the same as Elliot."

"Musicals are always about the first moments that prove why they are musicals," he continued. "Kate, our lead character, the mother, is singing a lullaby to her pregnant belly and the camera pushes in on her pregnant belly and that is our entrance into a whole other world where we see a mysterious little girl in a rowboat in the middle of the ocean, looking up at the moon and hearing that song, hearing that lullaby come through the moon. It's the moment you realize there's this little soul, this life that wants to exist and be in the world and wants to reach the sound of that voice. She doesn't know what it means or who it is."

"It just sounds like love, and she wants to reach it, and that's sort of the moment that we connect the two worlds of our movie, the world of Molly and the real world that her parents are living in," Thomas said.

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Bays told Deadline that the film — executive produced by Tory Metzger, with producers Renee Witt, Jaren Ian Goldman and Jamal Daniel, alongside Bays and Thomas — would be "all live action," as he and his writing partner "really wanted to make it feel like the classic live-action fantasy movies of our childhood, things like Labyrinth and The Dark Crystal."

"As we were building off of this metaphor, it became, how do we show this journey? How do we visualize a soul trying to make it into the world?" Bays said. "For us, it felt like the journey of climbing a mountain. Molly is this little girl and the moon in the movie represents being alive and participating in the world. It's her journey, trying to get to the moon."

"Around that, we built this magical fantasy world that we cut back and forth from, that interacts with the real world in surprising ways," he added. "We see the fantasy journey and the friends she makes along the way. There's a knight in shining armor. There's a talking bunny that she meets in the forest. There's a monster that she has to face. It's a real hero's journey for her."

Bell, 40, expressed her joy over the film on social media Thursday, sharing a link to the Deadline article and writing, "I am so excited for this project!!!!" Bell and Groff's Frozen co-star Josh Gad commented on the post, "Yesssss!!!!🔥🔥🔥🔥🔥."