The Other Woman co-stars stopped by NBC's Late Night Thursday, where they told Seth Meyers how they managed to pull a fast one on the 21-year-old blond bombshell. "It seems like you guys had fun working together and you had a little bit of fun together on a flight," the 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."
"She's like a teenager," Mann said simultaneously.
Smirking, Meyers said, "Whereas you are adult women who draw on people's faces."
So why did Diaz and Mann also sport black ink above their own upper lips? "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." Mann was bummed when Diaz decided to remove Upton's mustache before she woke up and saw it. "I'm like, 'No, just leave it on. It would be so awesome in the morning when she wakes up.' And she wiped it off."
"I washed her face while she slept," Diaz revealed. "She didn't move."
Diaz, 41, and Mann, 42, tend to misbehave more than Upton. "Any time we go out, we're always like, 'C'mon, let's go!'" Diaz said, doing a spot-on impression. "And she's like, 'I'm going home. I'm tired.'"
For more from the funny women—including why Mann "broke out in hives" while kissing co-star Nikolaj Coster-Waldau, who plays her husband in The Other Woman—watch the video above now.
(E! and Late Night are both part of the NBCUniversal family.)