'Black Swan' put Natalie Portman and Mila Kunis' friendship to the test

After pirouetting for hours on the set of "Black Swan," Natalie Portman would sometimes remove her pointe shoes, towel the sweat off of her brow and be met by a disapproving critique from director Darren Aronofsky.

Darren would tell us things about each other to try to make us jealous.

The young women are vying for the lead role in "Swan Lake," and while Nina can perfectly encapsulate the virtue of the white swan, she struggles to convey the sinister, sexual nature intrinsic to the black swan that seems to come naturally to Lily.

Aronofsky, the filmmaker behind "Requiem for a Dream" and the 2008 Mickey Rourke comeback picture "The Wrestler," had his own foes to overcome to get "Black Swan" made.

The fluidity of that relationship culminates in a heated sex scene between the young women, which is teased in the movie's trailer and has for months been the subject of media fascination.

Kunis said Aronofsky promised the actresses the film wouldn't leave his hands until it was released so that the scene wouldn't go viral on the Internet.

Crew members had their cellphones confiscated so that they couldn't take any photos of the steamy segment.

[...] Kunis, who with the rest of the "Black Swan" cast has spent the last couple of weeks promoting the film, said she was irritated that she had received so many questions about the racy moment.

"How people walk away from a movie like this and the first question out of their mouth is 'Is it uncomfortable making out with your friend Natalie?' -- it's unfortunate," she said in a separate interview a few days later.

Kunis is starring in "Friends With Benefits," while Portman is in "No Strings Attached."

Even as the film struggled to get off the ground because of financial issues, Portman began training five to eight hours a day with a ballet instructor.

At a certain point in...