The flick follows Julianne (Roberts) and Michael (Mulroney), two friends that vowed to marry each other if they were still single at age 28. Just before Julianne's 28th birthday, Michael announces that he's set to marry 20-year-old Kimmy (Diaz). Michael's sudden engagement makes Julianne realize that she's in love with him and, with the help of her best friend, George (Everett), she decides to ruin his wedding.
"It was, like, a huge break for me," Diaz, 46, gushes of landing the role.
The beloved nature of the film has only grown throughout the years, with Diaz's own sister-in-law, Nicole Richie, even gushing over Diaz's involvement.
"My sister-in-law is obsessed with this movie. We went to Chicago, like, a year and a half ago, and she took me to every single [location]," Diaz reveals. "She’s like, 'Remember when you were walking down the street right here and then…' It was so much fun. I was like, 'Yes, I think I do.' She’s like, 'I do, and it really means a lot to me, so I would like for you to pretend like you do.'"
Everett, too, has a special relationship with the film, one he looks back on with fond melancholy today.
"We all got on so well straightaway. And everybody clicked on screen straightaway, and you could feel that," Everett, 59, says. "And for me, it was magical. But the last time I saw it, it kind of made me cry just thinking of how magic that time was, that summer."
For his part, Mulroney, 55, admits that he "wouldn't give this movie up for anything."
"I liked that he was the lead in the movie and Julia Roberts liked him," Mulroney quips. "I liked those, like, obvious elements, but he had his own little story. He was a sportswriter and he was in love in ways that many people still argue with me about."
Meanwhile, Roberts, 51, signed on to the movie because she thought "it was really clever and just funny."
"All the physical comedy I loved. Lots of falling down and falling through things, falling all over myself, falling over Dermot," she recalls. "The scene, for me, that made it feel so authentic and earnest is when I finally tell Dermot’s character, 'Pick me. Let me make you happy.' Just that line: That’s just so succinct and sweet and meaningful."
Another standout scene in the movie came when Julianne, Michael and Kimmy went on a karaoke date, an effort by Julianne to embarrass Kimmy.
"We staged it as a real karaoke song, where the lyrics appear in front of you on all the monitors," director P.J. Hogan explains. "So I shot it live. Cameron just botched her way through the song, and the worse she got, the better the scene was. But then Cameron was so game that the applause started to become real."
"I was terrified to do that scene, for real. I allowed the true terror of singing in front of people to be alive in me. I wanted to run and hide, and Dermot kept me there," Diaz praises. "He said, 'You can do it, you can do it.' In the scene I’m just staring at him the whole time because he’s looking at me like, 'You’re okay. You’re not gonna die.' And I was like, 'But I’m dying.'”
One of Mulroney's best memories from making the film came when he and Roberts filmed a scene where Michael and Julianne take a ferry ride together.
"We’re going under numerous bridges, so pretty much every bridge or maybe every other, somebody leans down and yells, 'Julia!' during the filming," he recalls. "We’d either pause or just blaze through like you do. Then, like the eighth trip down the river somebody yells, 'Hey, Dermot!' and I was like, 'Yes!' I look up and it’s, like, a friend from college, which didn’t really count. I go, 'Hi, John.'”
The movie was originally supposed to end in the classic rom-com way, where Roberts, as the leading lady, lands her man against all odds. Test audiences, though, rejected that conclusion and thus, reshoots began. The film ended up grossing $127 million.
"One of the studio executives called it 'the $40 million reshoot,'" Hogan recalls. "I said, 'But it didn’t cost $40 million.' He said, 'No, that’s what you’ve added to your box office.'”
"Yeah, we needed a little bit more of an adversary," Roberts agrees.
"If Kimmy didn’t stand up for herself, it felt different for the end of the story," Diaz chimes in. "It wasn’t as gratifying."
Mulroney and Roberts have gone on to maintain their real-life friendship since making the movie, also starring together in August: Osage County in 2010 and Amazon's Homecoming last year.
"He’s my pal," Roberts told ET last year. "It’s been such a long time we’ve been together, this is our third thing together, and... it’s one of the reasons why being in the business so long is so fruitful, when you can return to relationships."
Mulroney wholeheartedly agreed, calling Roberts "exquisite."
"We’ve remained friends all these years and so, it’s not just working with one of America's greatest actresses, most endearing beauties, it is that I’m working with a friend of mine and these are really long, really beautifully written directed scenes," he said of Homecoming.
Watch the video below for more on the long-time friends: