Katharine McPhee Fitted for Nicole Kidman's Baby Bump

Call it the battle of the bumps: For pregnant roles in upcoming films, Katharine McPhee and Debra Messing will both don faux bellies, but only one will be brand new.

Messing insists she has been fitted with an original bump, but McPhee happily told PEOPLE that for Adam Sandler’s House Bunny she will wear a Nicole Kidman hand-me-down.

“I tried on [Knocked Up star] Katherine Heigl‘s belly. I tried on Nicole Kidman’s belly. And they said, ‘Oh, this one fits perfectly. We don’t need to try any more.’ I was so happy, because I didn’t have to sit through hours of prosthetic fitting,” the Idol runner up explained at the Wildlife Rescue Center of the Hamptons Benefit.

“There was nothing wrong with Katherine Heigl’s belly,” continued McPhee. “But every stomach is different. It’s light foam, but it makes you sweat. Hiegl’s felt funny on my stomach and sat higher. [In this project], I’m in my ninth month, so I should be hanging kind of low.”

Dispelling any possible pregnancy rumors, McPhee was enjoying a glass of red wine and the company of her boyfriend, Nick Cokas, 42. “In Stuff magazine, they said I want to have 15 kids.” She added, “I was obviously exaggerating.”

Meanwhile, Messing is set to star in a new version of Claire Boothe Luce’s The Women from Mick Jagger’s production company.

PEOPLE caught up with the actress at an Agas & Tamar jewelry event in Manhattan. “I play Edie Rosenberg, the woman who has the kids, perpetually pregnant, the earth mother. And, yes, I have to wear a pregnancy pad,” Messing said. “But I understand that mine was being custom-made … especially to fit me.”

Messing begins shooting in three weeks, and when asked if she thought she’d get to meet Mick Jagger, she answered, “probably at the premiere.”