Judd Apatow works, parents on set

Judd Apatow's new movie "This is 40" isn't for the under-17 crowd, so how does he deal with his two young daughters, Iris and Maude, being part of the cast?

His way around this parenting minefield, Apatow told CNN, is open communication.

"It's tricky, because kids see everything. This idea that we're shielding kids with an R rating is just the funniest lie," Apatow told CNN. "They watch everything on YouTube. As soon as you leave the room they're watching every show they shouldn't on television. It becomes more about talking about it with them and having a relationship where they'll ask you questions. Or maybe even listening to you if you tell them not to watch it. But, they can watch it anyway."

Yet there are times when he'll draw a line. "Sometimes, I'll say, 'Maybe you don't need to see the "Chucky" movies. Wait until you're older. That's a nightmare machine for you.' And if you have that relationship, they'll censor themselves," he continued. "You know our movies are adult-themed, but they're smart kids and I cover their eyes during the two or three bad parts, and they can handle it."

The reason he casts his daughters to begin with, he told the Hollywood Reporter in a recent issue, "is to get a level of detail that other people can't. People with existing relationships allow you an incredible opportunity to show truthful human behavior." So when his wife and leading lady Leslie Mann "kisses the kids, you feel the love."