In the psychological thriller, Portman and Kunis played ballet dancers, who were competing to play the lead role in a production of Swan Lake but according to the actress, Aronofsky wanted the on screen rivalry to translate into real life competition.
"He'd say, 'Oh, Mila is doing really well on her stuff. She's so much better than you'," Portman said in an interview to Vogue.
"Darren would tell us things about each other to try to make us jealous. I think he was trying to create a rivalry in real life between us."