Sundance: Ellen Page Wrote a Song to Soothe Her Baby Co-Star in 'Tallulah'

"I really considered stealing [a] baby and didn't, but wrote a movie about it instead," said 'Tallulah' writer-director Sian Heder.

Ellen Page — actress, activist ... songwriter?

Between feedings of Cheerios on the set of Tallulah, the star spontaneously penned a new song to pacify her co-star: a 15-month-old baby. "'I am a horse, riding on a turtle,'" she told The Hollywood Reporter at the 2016 Sundance Film Festival. "Of course I made it up — that was all me! ... You had no choice but to be in the present moment, because you could never anticipate what your little friend's going to do."

Written and directed by Sian Heder, the film stars Page as a rootless young woman who impulsively takes a toddler from a wealthy, negligent mother and passes the baby off as her own in an effort to protect her.

It was inspired by Heder's time working as a nanny for mothers in Los Angeles. "I felt like they should've never been mothers — one in particular, who had never been alone with her toddler," she said. "I really considered stealing her baby and didn't, but wrote a movie about it instead."