FXX's It's Always Sunny in Philadelphia, the longest running show in cable history, just finished its 13th season and even so deep in its run the gang at Paddy's Pub still manages to surprise.

On Thursday's season finale, Mac (show creator Rob McElhenney) got a rare moment of personal growth, which the show has routinely rejected. The central conceit of It's Always Sunny is that Mac, Charlie, Dennis, Dee and Frank are not good people—they're the actual worst—and being the worst they never desire to change or become better in any possible way. Mac, however, has always been a slight exception to that rule. He's not as dumb as Charlie so he's able to realize his shortcomings, and he's not as willfully unwilling as Frank, Dee, and Dennis to be introspective.

Mac's sexuality has long been a running joke on the show.

A devout Catholic with a shitty upbringing—his dad is a psychopath and his mom is an alcoholic—Mac has always been in such deep denial about his attraction to men that the rest of the gang never takes anything he does or says seriously, dismissing his actions as just another desperate ploy for attention. That's exactly how they treated his transformation into a raging beefcake at the start of the season.

Mac came out at the end of the 11th season when a fateful encounter on a Christian cruise ship with a gay couple opened his legs and his eyes to a new world.

It also tested his faith in God and he soon went back into the closet. Then in season 12, Mac finally and definitively came out following some hijinks it's not really worth getting into here. Just know it involved a dildo exercise bike.

The point is, Mac came to accept his homosexuality, ending a multi-season arc and resulting in the most fleshed-out character on It's Always Sunny in Philadelphia. But still, this 13th season finale came as a true shock.

In "Mac Finds His Pride," the gang is participating in Philly's Pride parade and they want Mac to dance on their elaborate float. In one of many knowing commentaries on the commercialization and commodification of LGBTQ culture, they complain that they can't have a straight guy dance on the float or else "the press would murder" them. Frank (a never better Danny DeVito) is charged, to his chagrin, with recruiting Mac, who's experiencing an existential crisis about where he fits in as a gay man.

For purely selfish reasons, Frank tries to help Mac "find his pride." First they go to an underground S&M orgy and then a drag bar, but Mac doesn't feel like he fits in at either. Then it occurs to Frank that Mac will never feel complete until Mac comes out to his currently incarcerated dad (Gregory Scott Cummins). While visiting him in prison, Mac is unable to get out the words, and instead his dad convinces himself that Mac has "finally" knocked up a girl. When Frank sees a woman exiting Mac's apartment and Mac putting back on his shirt, he, and I, assume that Mac is going back in the closet. After all, that's happened before. The entire time I just kept waiting for the other shoe to drop—for Mac to admit that he's not gay, despite all the evidence to the contrary.

Throughout the episode, Frank claims that he just never "got" Mac. An old-school bigot, Frank is the last person you'd expect to set Mac on a path of self-discovery. But Frank is able to find empathy for Mac thanks to a hilarious subplot involving a bloody nose and the increasingly bizarre tactics he employs to stop it, which only serves to make his face more and more comically grotesque. Once he just releases the blood, however, he realizes what Mac must do.

"Sometimes you got to let the blood flow" Frank says to Mac, "in order to start the healing. Some cuts you just can't plug up." Frank goes on to tell Mac that he needs to let out what's inside of him or he'll be in agony for the rest of his life. Here I expected Mac to agree to dance on Paddy's float—the show loves an elaborate build up to a simple gag—but Frank wants him to forget about that and focus on his true release: coming out to his dad.

It's Always Sunny has had musical vignettes before, most memorably season four's "The Nightman Cometh," but they've always been used for comedic effect. This time, however, there was no punchline. Mac and Frank go back to the prison and stage a show for the prisoners. Mac introduces the show by telling his dad that he's gay and immediately launching into a gorgeous interpretive dance with the woman last seen leaving his apartment—his dance partner. And that impressive physique he built was more than just for show, but for function.

Mac had tried to explain to Frank earlier about what was going on inside of him: "There’s like this storm inside of me and it’s been raging my whole life."

"And I’m down on my knees and I’m looking for answers and then God comes down to me and it’s a very hot chick."

"And she pulls me up and we start dancing.”

Frank's initial response was, "The Catholics really fucked you up." Which...valid.

Mac's dad walks out in the middle of the performance, which is part of the performance itself. The rejection he receives from his dad is mirrored on stage, but the God he is dancing with ultimately accepts him. They end their pas de deux with Mac crawling into God as she whispers, "It's okay, it's okay, it's okay." And Frank, well:

And then it ends. The audience stands applauding in awe and the show cuts to the credits. There's no joke, no parting quip. That's the truly shocking bit about this entire episode. It's such a dramatic, uncharacteristic, and frankly adult way to end an episode, let alone a season. Over a decade in and It's Always Sunny has finally grown up.

But this show has always been way more than what it seemed, from its very first episodes. It's not just gross-out humor, over-the-top bits, and edginess for the sake of edginess—there's a wit and a wink to everything they do. It doesn't always work, but when it does, It's Always Sunny in Philadelphia proves why it's the longest running show in cable—and with its 14th season, the longest running live-action sitcom—and why it's still one of the best shows on TV, period.

Check out the full dance sequence below.