Natalie Portman and Mila Kunis say their Black Swan director tried to instigate a rivalry between the two that would strengthen their on-screen performances Speaking toVoguein an interview to markBlack Swan's 15th anniversary, the director himself noted he tried to "make them argue" But his plan was foiled due to the tight bond between Portman and Kunis, who realized quickly what he was up to Natalie PortmanandMila KunissayBlack SwandirectorDarren Aronofskytried to stoke a feud between them while on set, in order to mimic their on-screen rivalry. Speaking withVoguein a new interview to mark the 2010 film's 15th anniversary, the 56-year-old director said: "My take is that I was trying to be a sneaky director and make them argue. Mila and Natalie both realized very quickly what I was doing and made fun of me, so it quickly became a joke that we all understood. They're both very clever and were instantly privy to whatever trick I was playing." Kunis, 42, and Portman, 44, played rival ballerinas who were competing for top billing in a stage production ofSwan Lake. Kevin Mazur/WireImage Speaking to the outlet, the actresses said Aronofsky's plan didn't work because they figured it out. Said Portman: "I remember being separated from Mila and that we weren't in the same space a lot when we weren't shooting." But when Aronofsky would try to goad Portman into criticizing Kunis, she would instead say things like, "She's so f------ talented and I love her so much and I'm happy she's doing a great job!" Kunis added: "Darren would tell me, 'Nat is working really, really hard. She's not even taking Saturdays and Sundays off.' Then I would text Nat and she'd be like, '…No, I'm not?' I think that's how we figured out what Darren was up to, but it was all in good fun." Never miss a story — sign up forPEOPLE's free daily newsletterto stay up-to-date on the best of what PEOPLE has to offer, from celebrity news to compelling human interest stories. Elsewhere in the interview, Kunis spoke about the intense preparations required of her to get into character as Lily, the seductive rival of Portman's character, Nina. "My prep was a lot of dancing and very little eating — which I know you're not supposed to say, but it's the truth. I drank a lot of broth and danced for 12 hours a day," she told the outlet. "We were only supposed to have three months of prep before filming started, but we lost some financing, so that got extended to six months while Darren tried to find money," Kunis continued. "It sucked for Darren, but Nat and I were so happy because we had three extra months to dance." The film, which had a modest budget of $13 million, went on to pull in nearly $330 million worldwide at the box office. Portman won the Best Actress Oscar for her mesmerizing performance. Fans can catch the movie on the big screen once again for a limited time this month. On Aug. 21 and Aug. 24, a newly remastered version ofBlack Swanwill be shown on IMAX screensacross the country. Read the original article onPeople