Matthew Lawrence, who played Robin Williams’ character’s son in Mrs. Doubtfire, revealed the late actor told him to not “ever do drugs” due to his own.

Dory Jackson is an Associate Editor for PEOPLE’s digital TV team. While at the brand, she’s had the opportunity to interview a long list of celebrities, from Kate Hudson to Pierce Brosnan to Billy Porter. She has also helped recap popular TV shows like ‘The Real Housewives of Beverly Hills,’ ‘Sister Wives’ and ‘Vanderpump Rules.’ The New York-based Maryland native graduated from Randolph-Macon College in May 2016 with a focus on Communication Studies and Journalism. She came to PEOPLE in March 2021 after working at a number of major news companies, including Newsweek and Us Weekly.

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Matthew Lawrence still thinks fondly about his time working with Robin Williams in Mrs. Doubtfire.

During his appearance at the first-ever ’90s Con on Saturday, Lawrence opened up about the lessons he took away during their experience shooting the 1993 film.

“He was the first adult who really let me in on his condition. Like, full-on let me in,” the 42-year-old said. “I mean, as bright as he was on camera — I would go visit him in his trailer to talk to him — it was painful for him. It’s really painful for him. He didn’t hide it. He talked to me about it.”

Lawrence said Williams, who died at 63 in 2014 after taking his own life, had given him “a gift” through a very profound piece of advice.

“‘Don’t ever do drugs. Especially cocaine,'” Lawrence recalled Williams saying. “He was very serious. He was like, ‘You know when you come to my trailer and you see me like that?’ He’s like, ‘That’s the reason why. And now I’m fighting for the rest of my life because I spent 10 years doing something very stupid every day. Do not do it.’ I stayed away from it because of him.”

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Lawrence continued to praise Williams, saying the late actor was a big reason he landed the part of Chris Hillard — Williams’ character’s son — in the iconic film. Initially, the Boy Meets World alum was “a hair away” from nabbing the role.

“There was another strong choice that everybody else wanted. The studio wanted this other boy … I don’t know who it was, I was only 9 years old. But I did start to sense that something was up because there was like this little pause and little awkwardness and I was always the quiet one,” he said.

During the pair’s screen test audition, however, Lawrence said that Williams wanted to “do something” that would help catapult him to the top choice.

“He very secretly reached behind my back and pinched me so hard,” he recalled, making a sound indicating his pain at that moment. “The studio started bawling and wept. I got the role because of that little moment over the other boy. It was all Robin Williams. ‘I know what I’m going to do to get this kid this job.’ Thank you, Rob.”

Sally Field, Pierce Brosnan, Harvey Fierstein, Robert Prosky, Lisa Jakub, and Mara Wilson also starred in Mrs. Doubtfire. Wilson, who was also in attendance at Saturday’s event in Connecticut, shared her own gratitude for Williams’ influence.

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“Robin had a massive influence on me,” said Wilson, 34. “He, during filming, would talk to me a lot about his issues with mental health and addiction. And I have had a lifelong struggle with anxiety and depression. So, we had those conversations.”

Added Wilson, “I think it was so good for me to realize that it’s okay to talk about this. It’s okay to be vulnerable. And it was really the first time that I had someone sit down with me and go, ‘I understand that you have anxiety, and you are not alone. You’re not just some weirdo freak who has something going on that nobody’s going to understand, that everybody’s going to reject you for.’ Like, this is okay and there are things you can do, and you will be alright.”