Kate Upton, Cameron Diaz, Leslie Mann
See All Photos Nicholas Hunt/Patrick McMullan/Sipa USA

In the hilarious new comedy The Other Woman, three gals (played by Cameron Diaz, Leslie Mann, and Kate Upton) end up becoming friends after they come to the realization that they are all dating the same man (Nikolaj Coster-Waldau), leading to a series of laugh-out-loud scenes that entail the ladies plotting their revenge on said unfaithful bad boy. So it comes as no surprise that in real life, these three hoots are just as comical when they are around each other. We learned just that last night when we hung with them at a screening of the film, hosted by The Cinema Society, InStyle and Bobbie Brown at the Paley Center in New York City.

The gorgeous trio walked the carpet arm-in-arm, giggling, and hamming it up for the cameras. “I love to laugh. I think that life is hard, and there’s difficult points at anytime in your life and laughing is the best medicine,” says supermodel Upton, who made her debut acting performance in the film.

And since she was a newbie and all, her more-seasoned co-stars made sure to break her in properly — with lots of pranks on set. “When she fell asleep, because she’s like a little teenager so she sleeps long and hard, Cameron and I were like, ‘what are we gonna do? What are we gonna do?’ And so we got her eyeliner and we drew a mustache on Kate’s lip and then drew mustaches on ourselves,” Mann says. “Then we decided to draw beards, little goatees, on her, so then we drew little goatees on ourselves and then we took pictures.”

And since both Diaz and Mann feel they have already had their fair share of bad dating experiences, they’re turning to Upton to be their romantic Guinea pig. “Kate is still so young we pretty much, we figure that she has a lot of mistakes ahead of her still, and so when she picks a guy that’s gonna cheat on her again she’s gonna call us and we’re going to get revenge on him,” Diaz jokes.

After a lovely cocktail hour attended by the cast, as well as other stars including a pregnant Doutzen Krous, Gayle King, Russell Simmons, co-host Bobbi Brown, and chef Katie Lee, attendees headed into the theatre for the screening, where an evening of laughter ensued as the girls continued to entertain the crowd on-screen.

See more pics from the InStyle party here in our gallery.

For more on our cover star Cameron Diaz, pick up the May issue of InStyle, available on newsstands and for digital download.