'Kit Kittredge: An American Girl' premiered in the Big Apple Thursday night, with JULIA ROBERTS -- the film's executive producer -- alongside the film's young star, ABIGAIL BRESLIN, and ET was there!

"I was giving birth a year ago yesterday [to HENRY], and [my sister] was taking care of this baby," Julia tells ET about LISA GILLAN, who also produced the film. "This is something that we feel influences and teaches in a really positive, interesting way."

So, is Julia's daughter HAZEL ready for her own American Girl doll? "She's on the cusp," says Julia. "We were just discussing which birthday -- four or five -- for her first doll."

The film's CHRIS O'DONNELL, JANE KRAKOWSKI, STANLEY TUCCI and WILLOW SMITH (alongside mom JADA PINKETT SMITH) were also on hand for the fun event!

Based on the hugely popular American Girl book series, 'Kit Kittredge: An American Girl' stars Abigail as a resourceful young girl living during the Great Depression whose bravery, compassion and determination help her solve a mystery that saves her family's home.

The movie opens in select theaters today (for a 10-day exclusive engagement in L.A., New York, Chicago, Dallas and Atlanta) before opening nationwide on July 2.