The 14-year-old actress is starring in "Little", which reverses the premise of the iconic 1980s movie "Big", which starred Tom Hanks as a young boy aged up to adulthood. In the new movie a company executive, played by Regina Hall, relives her life as a 13-year-old.
Marsai loved "Big" so much she presented her idea for the new film to "Black-ish" creator Kenya Barris, who helped her get it made.
"It was one of my most favorite films growing up," she told U.S. website The Root. "After the Season 1 finale of 'Black-ish', we told Kenya Barris about it, and he called Will (Packer - a film producer) and said: 'Yo, you know the girl who plays Diane on Black-ish? She has this dope idea!'"
Although "Little" is directed by Tina Gordon Chism, who co-wrote the script with "Black-ish" scribe Tracy Oliver, as it is based on an idea by the 14-year-old she is credited as an executive producer - making her Hollywood's youngest ever.
The teenage star's film means she has edged out another 14-year-old, "Stranger Things" star Millie Bobby Brown, in breaking the record, as the British actress is six months older and is producing a new film franchise about Sherlock Holmes' younger sister.
"Little" opens in cinemas in April, with the first trailer for the new film debuting on Wednesday, January 09.