Diaz and Leslie Mann stopped by "Late Night" Thursday, where they told Seth Meyers how they pulled a fast one on the Sports Illustrated model.
"It seems like you guys had fun working together and you had a little bit of fun together on a flight," the late night host said. "Tell us about this." "We did," Mann admitted. "Bad, bad girls!"
Meyers then showed a picture of Upton sleeping on a plane. "She was fast asleep, like right away, which makes me so mad because I can never sleep on flights," Mann said. "So Cameron and I were up and we're like, 'Yeah, what can we do?' She's like passed out and we decided to draw [a mustache]."
"I'm drawing on her and she does not wake up," said Diaz. "She's like a child. She's like a little baby."
So, when they started feeling guilty about their artwork, they decided to draw their own staches.
"I started feeling really guilty. I felt really bad after," Diaz admitted. "I was like, 'We can't take pictures unless we have mustaches as well.' So we have other pictures where we're drawing on each other's faces."
Watch the clip above to see how Kate reacted to the prank, and click "Launch Gallery" below to see her sexiest shots.