He's the funny guy behind Knocked Up and The 40-Year-Old Virgin. But his jokes usually bomb with daughters Maude, 14, and Iris, 10.

By Patty Adams Martinez

Q. Were you always a comedian?A. When I was in third grade, I'd draw guns on my underwear, then jump out in my briefs in the locker room and say I was Captain Underwear. Can't say it was that witty, but I was very committed to it.

Q. We imagine the wisecracks are nonstop at your house.A. It's a close race, but I'd say Iris is the funniest. The other day she was listening to Maroon 5's "Payphone," and I said, "Nobody uses a pay phone these days." She said, "Unless you're in jail." You always appreciate a good line from a kid.

Q. And vice versa? Do they appreciate your comic genius?A. Everybody thinks their dad's jokes are corny. I don't get a free pass on that. In fact, Iris said to me once, "Most of your stuff isn't funny at all. But I'm always surprised you make it work." I thought that was a pretty sophisticated way of attacking me.

Q. Iris and Maude are in your new movie, This Is 40, along with your wife, Leslie Mann. What's it like directing the kids?A. Half my day is spent begging them to eat fruit and not M&M's. Otherwise they crash, cry and want to go home. Then there are days when the kids don't even realize we're shooting a movie. They just sit down, I roll film and they start arguing with each other about things like whether Iris is old enough to watch South Park. They'll go to war about that, and that's the scene.

Q. How do you explain all the cursing and sex in your films to them?A. My kids do hold all the cursing against me. But I tell them the characters talk like that because it's ridiculous, and that's what makes it funny. Cursing makes you sound stupid! As for sex, writing The 40-Year-Old Virgin brought up all sorts of questions—including "What's a virgin?" It's very difficult to go years without answering that question, but Leslie and I found a way to do it.

Q. Who's the favorite parent?A. Leslie. She starred in 17 Again with Zac Efron, so she had him call Maude at her birthday slumber party. All the girls went crazy. You can't top that.

Q. So your daughters' friends don't think you're cool?A. No. I get zero respect. I always think at some point they'll realize I worked on Superbad. But that never happens. I'm just the goofy guy picking them up at volleyball.

Q. Maude has more than 80,000 followers on Twitter. Are you one?A. Yes—that's how we know what's going on in her life!

Originally published in the January 2013 issue of Family Circle magazine.