L to R: Glenn Howerton as Dennis, Charlie Day as Charlie, Rob McElhenney as Mac, Danny DeVito as Frank and Kaitlin Olson as Sweet Dee.

Longtime fans of FX’s “It’s Always Sunny in Philadelphia” celebrate its morally bankrupt humor and the characters’ unapologetic selfishness. As such, the idea of a baby joining the Paddy’s Pub crew may be met with a touch of trepidation. Not out of any worry for the baby, understand, but for fear that lil’ snapper could stink up the show’s perfect formula.

Adding an infant to the series was not necessarily a forgone conclusion, mind you, even if Kaitlin Olson (who plays Sweet Dee)  happened to be pregnant throughout the sixth season’s production. Sitcoms have a long tradition of hiding pregnancies behind a wide variety of  plants, gigantic purses and under desks and dinner tables.

Then again, this is a show that takes serious, hot button topics such as gay marriage, divorce and animal rights and shellacs them in oddity and ridiculousness. How could they not find a way to turn Olson’s treasured condition into something the Paddy’s crew sees as preposterous, ugly and wrong?

But we’re getting ahead of ourselves. Although Olson and her husband and co-star Rob “Mac” McElhenney welcomed their son Axel Lee on September 1, tonight’s season premiere tackles gay marriage…and as one might expect of such a self-absorbed, shallow group, they don’t even seem to notice Dee’s expanding middle. In fact, Mac, Dennis (Glenn Howerton), Charlie (Charlie Day) and Frank (Danny DeVito) don’t even really bring it up until the Halloween episode, “Who Got Sweet Dee Pregnant?” Before that, we’ll experience “Sunny’s” uniquely idiotic takes on divorce, owning a boat, and pursuing celebrity via podcasting.

We caught up with Olson, McElhenney and Howerton in Hollywood this summer to ask them about the ways in which adding a bundle of joy to the Paddy’s crew could affect the show’s dynamic.

IMDb: How in the heck is a baby going to fit into this show?

Kaitlin Olson: You’ll have to wait and see. But I will say that I think that they did a really amazing job of writing it in and dealing with it in a way that you haven’t really seen before.

Does she have the baby this season?

Olson: Yes, but you’re not going to see a big pushing scene. You’re not going to see my vagina, if that’s what you’re asking.

I can imagine that you must have looked at all the ways this has been dealt with on television. There’s the disappearing baby…

Olson: Right. There’s also that big pushing scene, and the screaming…that was originally, for one reason or another, going to be in there. But they took that out all together, because it’s just so cliché at this point.

Are we ever going to find out who the father is?

Olson: Yeah, you will.

Is it someone we know?

Olson: I’m not answering anything else! It could be. There are all kinds of options. It’s very fun, trying to figure out from all the options, who it is.

Is the answer absolutely frightening?

Olson: Um, no. I wouldn’t say it’s frightening. In real life, it’s frightening because I’m pretty sure that Rob’s the father, but we’ll see when it comes out.

One of the things that’s clear in the show is that you seem to keep track of current events that people are talking about to do your own take on them. Are there any topics that…well, I won’t say that you wouldn’t do, but I must imagine there must be topics that would tougher to take on than others.

Olson: I would say that rather by process of elimination, we pick topics that we say, “Ooh, we haven’t seen that dealt with before.” And the ones that are vetoed are ones that we say “It’s been done before” or that we decide is just shock value and we don’t have an interesting take on it.

Gay marriage is a subject that’s pretty close to our hearts anyway, so we were really excited to find a way to work that in. And of course, we make fun of the side we don’t agree with. So that was a really fun one, because all of the characters have different points of view about it, and are using ridiculous logic when they’re discussing it. It’s a social commentary that you can laugh at, you know what I mean?

IMDB: (to Glenn Howerton) Are you concerned at all about what having  a baby join the group might do to the dynamic of the show?

Howerton: Yeah, there was a lot of discussion in the group…about what it would do to the show to have a baby on it…But there are a lot of pros, too, to having a baby in the cast, to having a baby be a part of our lives. It’s a very real thing, and it changes you and it alters you. You have this other life that you have to take care of. How do you deal with that when you’re a very selfish, self-involved person? And does it change you? If it does, in what ways will it change you?

Interesting. Do you think the answer will be for them, “Not at all”? Will the kid grow up to be as selfish and self-involved as the characters are – and, possibly, illiterate?

Howerton: Yeah…well, I can’t give too much away where that’s concerned. In the season finale, she has the kid…That was the other big challenge about this, was, there have been a million sitcoms and dramas where one of the main characters has gotten pregnant and had the child. But even the episode itself of her having the baby, that was a huge challenge for us. That’s been done a million times.

So how do we, who always set out to show you something that you’ve never seen before on television, how do we show you something different with this storyline that’s been done a million times? I’m very proud to say that we deal with it in a way that, I think, has never been done.

Rob McElhenney: When we were in the writing process, and we spent weeks mulling over how we were going to handle this. Because it just inherently changes the dynamic of the show. There’s just no way to address having a baby that doesn’t change specifically storylines or the characters of whoever is having the baby. And I think that we finally figured out a way to solve the issue in a way that doesn’t change the dynamic of the show, and that is a fresh and different approach to an age-old issue in sitcom writing.

Because the truth is, there are only so many baby storylines that you can do once a woman has a baby…but unfortunately, the baby doesn’t do anything but sleep and eat. So you can’t revolve any more storylines around his needs, because his needs – or her needs – are to sleep and eat. That’s it! And you can’t just have the baby somewhere else, because you need to account for where it is.

So, Dee’s a main character, and if she’s out gallivanting around, people are going to say, where’s the baby, what’s happening with the baby? I believe that the American public will allow for a lot of gaps to be filled, in terms of logic, but that is not one of them. I believe that. I believe you have to suspend your disbelief when you’re watching movies and TV, specifically TV. This is something we never question, but on TV, people are constantly coming over to people’s houses to talk with them when, in real life, they’d just call them.

But in our suspension of disbelief, we say, “Who gives a shit? It got them in the same room.”…And yet, I think that ultimately the reason that we are successful is because we do manage to fill in the logic gaps as much as we can.

IMDB: (to McElhenney) As a writer and the show’s creator, do you think that having a baby will change your creative sensibilities in terms of steering “Sunny”?

McElhenney: I think it’s the opposite, in terms of thinking the world is unsafe. I see a lot of parents reacting that way, and I made a vow to myself that I would not. That I will teach this baby, from day one, that that world is not a scary place,  that the world is a wonderful place and that it’s full of opportunities if we can trust in it and apply ourselves.

That said, I’m not going to not prepare him for the ability to defend himself in certain situations, or protect himself, but I feel like the culture of fear that we kind of live in and that I was raised in – and all of us were raised in, in some way shape or form – I feel like it’s really destructive and detrimental to us  realizing our true potential. If we’re taught from a very early age not to fear anything … you can take a more positive stance.

In terms of writing sensibility, I feel like it’s about approaching the world from a more positive outlook.

“It’s Always Sunny in Philadelphia” airs new episodes Thursdays at 10PM on FX.