Five years after writer/director Judd Apatow introduced audiences to Pete (Paul Rudd) and Debbie (Leslie Mann) in Knocked Up, their life is being revisited and explored much deeper in the honest yet hilarious look at marriage and parenthood in This is 40. Pete is struggling to keep his record label afloat, Debbie is hoping her clothing boutique will turn a profit, and their two daughters – 13-year-old Sadie (Maude Apatow) and 8-year-old Charlotte (Iris Apatow) – are just trying to navigate parents, school and boys, all while finding their way in the world together.

During a press conference to promote the film’s December 21st theatrical release, co-stars Leslie Mann and Paul Rudd talked about the toughest aspects of turning 40, the most difficult scene to get through without laughing, preparing for the film’s more awkward moments, relating to their character’s frustration with life, and how they felt about watching themselves in the film. Check out what they had to say after the jump.

Question: What was the toughest thing, personally, about turning 40, and how did you overcome it?

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LESLIE MANN: I think every day is different. Some days, I feel fine, and other days I feel like crying all day. I have lunches with my girlfriends, who just turned 40, and some of those lunches, we’re crying and screaming about our husbands, saying we want to leave them and run away. And then, other lunches, we’re fine and love our husbands and are happy with our lives. So, I’m not sure. I don’t know. I don’t have any answers. I keep asking women who are a little bit older, “When is this going to pass?,” and they’re like, “It doesn’t pass. It just gets worse.”

PAUL RUDD: I remember, as a kid, my dad always told me, “Getting older beats the alternative.” Although, now my father actually is the alternative, so I don’t know what he would say. He’s completely dead.

Leslie, does Pete and Debbie’s relationship feel very much like the relationship between you and Judd?

MANN: It’s what I would fantasize about saying to Judd. Debbie can say these things to Pete, but Leslie can’t really say these things to Judd. It’s fun to have this character to live through.

What was the most difficult scene to get through without laughing?

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MANN: Melissa McCarthy was the hardest one to get through. That was impossible. I’ve never experienced that. Maybe one time, I’ll crack up, and then I can hold it together, from then on. But with her, it was hours. We could not keep a straight face. Finally, we just gave up. Judd was using more than one camera, so we could just laugh. And the crew were all laughing. It was ridiculous. She’s just the funniest person, ever.

RUDD: I’ve seen people on tears before, but that was something otherworldly. People were leaving the room. Crew had to leave. It was impossible. And she just kept her composure through all of it.

Paul, your character is struggling with his business, but you seem to be doing better than ever. Have you had moments, where you felt like you really had to struggle with your career?

RUDD: Sure, yeah. Everything is a struggle. Everything is relative, too, so I still feel like I’m struggling, in many aspects. I’m not worried about paying my rent next month, but in about two months, we’ll see.

What is one of the worst jobs you’ve had?

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RUDD: One of the worst was that I glazed hams. I did that for about half a year. It doesn’t get worse. I was trying to get money to go to acting school. I was in college and I got a job. It was in Kansas City, before I moved to go to this theater school. I got paid in ham. No. I got paid a little bit more than the minimum wage. It was an all day affair. I would unload a truck at about five in the morning. I’d have to unwrap the ham and put it on a metal spit. There was a propane torch that hung down from the ceiling, and I had wrist guards to protect myself. I’d go back and forth between heating the ham, and then using a sugar sifter. I’ve had several bad jobs.

Paul, how did you prepare to do the very awkward scene that you have, with your legs up over your head, and has there ever been anything Judd Apatow has asked you to do, that you’ve just refused?

RUDD: I’m sure there has been.

MANN: He wouldn’t take off his shirt on the toilet.

RUDD: I’m not excited about any of it. I thought it would be funny. It’s embarrassing and horrifying, but in the context of the movie. What we’re all trying to go for is some kind of reality. If it’s funny, there’s certainly no room for vanity. I was laughing as I was doing it, while I was dying on the inside. The only way you can prepare for something like that is with a bottle of gin.

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Leslie, are you pretty much game for anything?

MANN: I’m pretty much game for anything.

Paul, as a husband and father yourself, could you relate to Pete’s frustration about life?

RUDD: Oh, yeah! Obviously, the situations are different, but there are certain aspects of marriage, parenthood, and all of that stuff, that seems relatable. We’ve spent years talking about all of this stuff. My wife and I, and Leslie and Judd have gotten together, had many dinners and talked. We did that going back to Knocked Up, so there are aspects of the character that are very much a part of me.

How do you look back on some of your earlier films, which have stood the test of time, like Clueless?

RUDD: It’s nice to be in anything that anybody sees or likes. If it’s something that has lasted, it’s great. People do still mention Clueless to me. I’m proud and happy that I was in it.

How did you both feel about watching yourselves in this film?

RUDD: Shooting it, I don’t feel too uncomfortable because it’s the character. I think definitely when it’s all done. Then, I’m like, “Oh, wow, that was a little much.” I think I land somewhere in the middle. I don’t have that thing where I’m like, “Oh, I can’t watch myself.” And I think I can be critical, in good ways. But, I don’t do it all that often, once the thing is done. It’s always surreal, the first couple of times.

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MANN: I like that [uncomfortable] tone, in a movie. The more uncomfortable, the better. The more truthful, the better. One of my favorite movies of all time is Broadcast News, and I love [Albert Brooks] sitting there sweating while he’s trying to read the news. That’s the greatest thing, ever. It’s so heartbreaking. It’s so uncomfortable to watch, yet so funny. It’s the perfect combination of everything. That’s my dream, to see something like that. That’s fun, to act and to watch.

What actually makes you feel uncomfortable then?

MANN: The only thing that made me feel uncomfortable in this movie is that scene where I’m laying in bed with Iris because it felt a little invasive. I don’t know why. I can do anything else. But that, for some reason, felt a little like it was crossing some boundary, just because everyone was sitting there watching me with my little girl, doing what I do with my little girl. I didn’t like that. But, anything else goes. I’m fine with anything else.

This is 40 opens in theaters on December 21st.