It's Always Sunny in Philadelphia It's Always Sunny in Philadelphia

Paddy's Pub isn't the best place to turn for child care: The guys of It's Always Sunny in Philadelphia once purposefully started serving underage kids to get more business, and  adopted a Dumpster baby to exploit as a TV star. But now that star Kaitlin Olson is pregnant in real life, get ready to see Sweet Dee with child this season.

"Ultimately we realized we were never going to be able to hide it, realistically," co-creator, executive producer, star and baby daddy Rob McElhenney tells "So we knew we had to embrace it and put it into the show."

Rob McElhenney and Kaitlin Olson expecting first child

Although the writers could have felt limited by the development, co-creator, executive producer and star Glenn Howerton says the pregnancy provided new opportunities for Season 6, premiering Thursday, Sept. 16 at 10/9c on FX.

"Why not put our own spin on that, the way we put our own spin on a lot of other things," he says. "It has been done so many times, it became very challenging for us to try and figure out something that hadn't been done a million times."

Olson, who's been married to McElhenney since 2008, says she was happy not to have to wear giant shirts and carry around boxes — TV's standard tricks for hiding an actress' pregnancy.

"Being able to write it into the show and document it has been really awesome," Olson said. "It just happened to work out perfectly where I was shooting during my second trimester and I felt really good."

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The cast and crew say the pregnancy will not be addressed in every episode, but promise a whodunit episode, in which the guys try to figure out who the father is, as well as a Dee-gives-birth episode this season. Just don't tell us that Mac, Dennis, Charlie and Frank will actually become — gasp — softies at the sight of Sweet Dee's growing belly.

"I wouldn't say that any of them are that compassionate," Olson says. "They do come around ... you get to see how they all kind of respond to it."

The series will explore domesticity in various ways this season, as Dennis will get hitched to his high school sweetheart. Both Dennis' surprise nuptials and Sweet Dee's pregnancy are recurring storylines throughout the season, which will also welcome guest stars such as Dave Foley, Jason Sudeikis, and Tom Sizemore.

"It was an interesting challenge for us to do something a little different, which is to have a storyline that continues through more than one episode," Howerton says.

The cast was tight-lipped on how Season 7 (the series' last on its current contract with FX) will address Sweet Dee's new addition.

"The resolution of the pregnancy, where we landed, is something no show has ever done, McElhenney says.