Kate Upton, Cameron Diaz and Leslie Mann became extremely close while filming 'The Other Woman'

Kate Upton is playing her biggest role yet in the movie The Other Woman, which is in theaters today. Actresses Cameron Diaz and Leslie Mann only have nice things to stay about their bombshell Sport Illustrated swimsuit model co-star, who is shockingly a little uncomfortable in a bikini.

Upton plays one of the three women being cheated on by the same guy. She told Fox News that, “Whenever I was in a bikini, I was feeling uncomfortable, because there was like 60 staring at me.”

Diaz and Mann praised Upton for her amazing performance, and killer bod. “She was amazing,” Diaz told FOX411. “She delivered above and beyond out expectation.” The three became close friends off screen after working together for so long, and Upton really appreciates the support the two women had for her.

When they saw that she was feeling uncomfortable during the bikini scene, Upton says that they would stand next to the cameraman and support her. She even wishes they could be with her during her Sports Illustrated shoots.

Diaz couldn’t believe how amazing Upton’s body actually was. “We got to see it firsthand,” she praised. “Y’all have to see it up on the screen.”

The three became so close that they even felt comfortable playing some pranks on each other. On Seth Meyer’s “Late Night” on Thursday night, Diaz and Mann revealed that they decided to draw a mustache on Upton while she was sleeping on the plane.

“She was fast asleep, like right away, which makes me so mad because I can never sleep on flights,” Mann told Meyers. “So Cameron and I were up and were like, ‘Yeah, what can we do?’ She’s like passed out and we decided to draw (a mustache).” Diaz added that she did not wake up as they were drawing. “She’s like a child,” she said. “She’s like a little baby.”

The two eventually felt bad and wiped the mustache off before she woke up, but they made sure to take some classic pictures of the star and even drew mustaches on themselves so they could take a hysterical picture.

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