It was her first film set and she recounted that she saw one of the crew members was being unpleasant to one of their colleagues and homophobia was suggested as the reason behind it.
Not understanding what that was at the time, Ricci get an explanation from Ryder who ended up getting Johnny Depp on the phone, who Ryder was dating at the time.
Speaking on Andy Cohen Live, she remembers he was very clear that Depp told her being gay was 'when a man wants to have sex with a man' and 'when a woman wants to have sex with a woman'.
She remembers that Cher was also part of the movie production, and joked that they 'should've run right over there' and just asked her about it.
Ricci remembers Depp explaining the whole thing to her 'very matter-of-factly' and keeping things in the 'simplest terms' so that she could fully understand what was going on.
She said: "Johnny is actually the person who explained to me what homosexuality was when I was nine.
"There was something going on on set and someone was not being nice to someone else. And they were like, 'Oh, well he might be homophobic.' And then I was like, 'Well, I don't understand what that is.'"
"And, and I was in Winona's trailer and she was like, 'I don't know how' so she put me on the phone with Johnny. And Johnny explained it to me."
Ricci will be part of the upcoming Tim Burton Netflix show Wednesday, which will follow the daughter of Gomez and Morticia Addams as she gets through school.
It was Ricci's performance as Wednesday in The Addams Family (1991) and Addams Family Values (1993) that really helped launch the popularity of the character.
As the classic Wednesday Addams, Ricci will be playing a new role alongside the part she helped make famous in the Netflix series, which according to lead star Jenny Ortega will run for about eight hours in total.
Ricci and Ortega will be joined in the cast by Catherine Zeta-Jones as Morticia Addams and Luis Guzmán as her husband Gomez.
While there's no release date as of yet for Wednesday, it's expected to drop onto Netflix by the end of 2022.
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