Former child star Mara Wilson is looking back at her time on the Mrs. Doubtfire set with her costar Robin Williams.

In an expert from her new book, Where Am I Now? True Stories of Girlhood and Accidental Fame — hitting bookstores in September 2016 — the 28-year-old shared an adorable set story that left her feeling "humiliated" in front of the late actor.

Mara recalled her six-year-old self having a "sex talk" with her mother one night before filming the movie. "I was bubbling with excitement, because I knew this thing, this big open secret, and I could not keep it in any longer," she wrote, according to Buzz Books.

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Mara and Robin in Mrs. Doubtfire.

She later approached one of the film's hairdressers to ask her if she'd "ever done it." Soon after, Robin — who was fully disguised as a woman for the scene they were shooting — approached the film's director and asked, "Did you hear that Mara was asking Virginia about sex?”

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To top it all off, Mara later boasted to the cast and crew that she knew all about sex! "Instantly, I felt humiliated, and worst of all, I knew I had brought it all on myself. I thought I might start crying," the actress wrote of the past, embarrassing incident.

Click through the gallery below to see the cast of Mrs. Doubtifre then and now!