It's not so much the graphic violence, the wild sex, or a lactating prostitute that earned an R rating for Shoot 'Em Up, a new film inspired by Hard Boiled and compared by some to Sin City starring Clive Owen, Monica Bellucci, and Paul Giamatti. It's the presence of a three-week old baby in some of the scenes.

"Going into it we knew that there was going to be trouble with the baby, so we worked with the M.P.A.A. ... There are no children and gunfire in the same scene," producer Don Murphy said at a press event in Manhattan yesterday. But the motion picture association doesn't have a "no babies were harmed" disclaimer, he joked.

Producer Susan Montford let on that "an animatronic baby with face replacements" stood in for the real tyke at times. And Owen said the baby moviegoers will see is actually twins. "They were cast before they were born. They were a few weeks old. It was amazing.... It physically changed things and we were very careful, respectful. It was very quiet, we didn't upset the baby, all the noises and the craziness were after the real babies were used."

And then there's the sex. Writer-director Michael Davis, whose former work includes a screenplay about sexual behavior pioneer Alfred Kinsey, has Bellucci playing a lactating prostitute. Asked about a scene where Owen's character manages to satisfy Bellucci's character amid a gunfight, the actress quipped, "Imagine a man that can do that—I would love to meet a man who can do that!"

Shoot 'Em Up! opens September 7.