The pair caught up with PEOPLE about some behind-the-scenes memories from their 1999 LGBTQ cult classic But I'm a Cheerleader ahead of Cinespia's Pride Month screening Saturday at Hollywood Forever Cemetery, where DuVall, 44, made a surprise appearance to introduce the film.
"You don't get to do movies that are actually that meaningful that often, that really speak to people and help them feel less alone and show them that they're not the only ones out there struggling with this kind of thing," DuVall said.
"And it still hasn't really registered for me, how significant it is. It's really hard to grasp," she added. "But that something we did so long ago as just insane kids basically had such a positive impact on people's lives, It's really cool."
"I knew that movie was so good. I knew it was special. I knew it was really unique," Lynskey, 45, noted.
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Directed by Jamie Babbit, the movie follows high school cheerleader Megan (Natasha Lyonne) as her parents ship her off to a conversion therapy camp called True Directions. While trying to "cure" her sexual orientation, she soon falls in love with bad girl Graham (DuVall).
Lynskey played fellow camper Hilary, and the movie also featured some memorable performances from the likes of RuPaul, Michelle Williams, Julie Delpy, Cathy Moriarty, Mink Stole, Bud Cort and Eddie Cibrian.
Although the film's subject matter has since become a hotly-debated topic, with multiple states outlawing conversion therapy as the practice has been proven harmful and ineffective, Babbit's colorful, camp direction made the film a queer romantic comedy for the ages.
"It felt like the best way to deal with the topic because it is something that is so horrific," DuVall said. "And so it's such a delusional practice and I think the way Jamie handled it with the right amount of humor, but also shining the light on just exactly how absurd it is. Holding a mirror up to it in such a smart way."
"It was such a smart way to tackle that subject. It's smart to make it a satire and make it so absurd and so campy and over the top and colorful, and it's making fun of the basic idea of conversion therapy," Lynskey added.
Before filming began, DuVall and Lynskey bonded with Lyonne, 43, at a Kiss concert on Halloween as the latter two starred together in Detroit Rock City, which was about teen fans of the rock band. "We had a very crazy night," Lynskey recalled.
"That Melanie did not want to be a part of," DuVall quipped. "Melanie wanted to go home but the place she was staying, she did not have keys. So we drove her back to the house and she couldn't get in. And then she was just trapped with us."
They hopped from party to party before ending up at a casino at 6 a.m., but Lynskey forgot her passport, so they couldn't get in.
DuVall noted that she previously met Lynskey while working as a barista. "I had just seen Heavenly Creatures. And she came in to the coffee shop and I was like, 'Oh my gosh, the girl from Heavenly Creatures.' And I gave her a free coffee and told her I thought she was great," she recounted.
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"That's the first time anyone ever gave me a free thing," Lynskey said.
The pair remained close friends, even considering each other their chosen family. "Melanie is one of the closest people to me and one of the most important people in my life," DuVall explained.
"It feels like family, but beyond. It's like a lifetime bond," Lynskey added. "I don't know what I would do without you. It's crazy. You're just one of the most important people in my entire world and you have been for so long."
Get tickets to Cinespia's summertime screenings on their website.