For the better part of its time on air, “It’s Always Sunny in Philadelphia” was perhaps  television’s best-kept secret. The travails of the gang became increasingly prurient and outrageous, and it was a rare example of a show for which each new season was better than the last. Practically no other comedy, save “South Park,” would have the base ambitions to revolve plots around such concepts as literally having sex with other people’s mothers or welfare-induced crack addictions, much less the dexterity to pull them off.

Season five, though it certainly didn’t disappoint the “Always Sunny” fan base, was the first to exhibit any diversion from the “just a bunch of average guys making the show we always wanted” formula. That’s not to say that “Always Sunny” softened up (see “The D.E.N.N.I.S. System”), but its success was often tempered by conspicuously placed bottles of Coors Light and strained trips to Dave & Buster’s. “Always Sunny,” fans feared, wasn’t necessarily going corporate, but somewhere equally worrisome: mainstream.

Season six kicks off with “Mac Fights Gay Marriage,” where we find Mac, well, fighting gay marriage. After his formerly transexual ex-significant other receives surgery, Mac feels inadequate as soon as he discovers that she has married another man. And in classic Mac form, he blames this unfortunate situation on the institution of gay marriage, because an erstwhile transexual marrying another man is clearly wrong, as illustrated by his pushing two electrical plugs together. It’s a typical example of “Always Sunny” inverting the concepts of a contemporary issue, as we later find Charlie and Frank plotting to marry, an attempt to exploit gay-marriage benefits justified as “two cool straight dudes marrying each other.”

Some of the riffs are predictable and begin to drag, but the little things work well: Dennis quickly sours on the rushed marriage between him the hilariously-named Maureen Ponderosa, bemoaning her kitty-cat sweatshirts; Charlie shares some “alley almonds” that he found outside Paddy’s with the gang; Dee and Mac struggle to have a conversation when she tries to keep from vomiting and triggering Mac’s gag reflex.

Though the gang’s usual shenanigans haven’t gone away, neither has the product placement. Dennis’ breakfast with Maureen takes place at Subway, where they drink Seattle’s Best coffee and various promotional items in the background do little more than distract. Not only is the setting forced, but Subway seems like the exact t place Dennis or Frank would end up setting aflame for bringing its corporate ass to compete in the breakfast market. But thankfully it’s those antics that still dominate the show, and as long as they keep coming, Dennis can go on Jared diet if he wants to.