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Joey L./FX

It’s Always Sunny in Philadelphia star and creator Rob McElhenney has found a warm reception for his show’s singular brand of comedy.

It’s the second-to-last day of principal filming for the seventh season of FX’s hit comedy It’s Always Sunny in Philadelphia, and star Danny DeVito is shoveling salami into his mouth while reciting nonsensical poetry about deli meat. It’s not a particularly surprising scene for anyone who’s watched the irreverent, oddball sitcom, currently airing on Thursday nights.

The sound of a baby crying off-camera, however — now that’s enough to turn a few heads.

The whimper belongs to Axel, the 13-month-old son of series stars Kaitlin Olson and Rob McElhenney; the couple met on the show and married in 2008. Turns out, Axel is a regular presence on the set. So, too, are Mary Elizabeth Ellis and Jill Latiano — the wives of stars Charlie Day and Glenn Howerton, respectively — who’ve both appeared on the show and are, coincidentally, also expecting their first children. For such a puerile show, it’s a pretty familial environment. And just where does DeVito, the show’s veteran thespian and a father of three, fit into this dysfunctional brood? Jokes McElhenney: “He’s less of a father figure and more of a little-brother figure — one that I have to keep an eye on to make sure he doesn’t get in trouble.”

McElhenney, the lone Philly native among the cast, created the show with ?Howerton after getting to know him at a string of auditions in the early 2000s. And though his weight may be of national concern these days (he packed on 50 pounds for the current season), he remembers when attention was much harder to come by.

“The first few seasons, hardly anybody watched,” he says. “But anybody that did seemed to dig it, and anybody who didn’t dig it really hated it. That was exactly the kind of work we wanted to do: something polarizing.”

Despite the slow start, Sunny has since exploded into a full-fledged pop-cultural phenomenon. Rare is the sporting event or music festival that doesn’t see an appearance from Green Man, a spandex-clad superfan made popular by Day’s Charlie. A 2009 six-city tour of the show’s “Nightman Cometh” musical sold out in hours (there’s talk of a second run next year). And in August, a deal was reached to keep the show going through at least a ninth season.

For his part, McElhenney knows how good he’s got it — not just from a professional standpoint but from a personal one too.

“No matter how long my day is — if I leave at 6 and I’m not home until 9 — I get to spend it with my wife and my kid,” he says. “It doesn’t get any better than that.”