The Best Season Finale In It's Always Sunny, According To IMDb

It's Always Sunny in Philadelphia has had some seriously weird, wild season finales, but this season four closer has proven to be the most popular among fans.

According to ratings by fans on IMDb, the season four finale "The Nightman Cometh," which follows a pretty incredible season to boot, is the show's most popular closing installment. In the episode, Charlie (Charlie Day), the janitor at Philadelphia's downtrodden Paddy's Pub — who, despite his illiteracy, is a piano prodigy — writes a musical called "The Nightman Cometh," based on a song he penned earlier in the series about the virtuous "Dayman" and his natural nemesis, the "Nightman." 

After he enlists his cohorts Mac (Rob McElhenney), Dee (Kaitlin Olson), Dennis (Glenn Howerton), and Frank (Danny DeVito) to star in the show, the gang is off to the races... and eventually, the reason for Charlie's sudden desire to pen a musical comes to light. From the shoddy props to the gang's utter inability to hold it together during their live performance, here's why "The Nightman Cometh" is far and away the funniest season finale of It's Always Sunny in Philadelphia.

Naturally, when Charlie first tells his friends about the new musical he wants to stage, everyone wants to know what the angle is — particularly Mac, who wants to know, "who is this versus?" However, since every single member of the gang is openly desperate for fame and attention, they all agree to play pivotal parts in "The Nightman Cometh."

Mac stars as the nefarious Nightman, immediately ruining Charlie's vision by insisting that he'll wear cat-eye contact lenses and do karate moves the entire time. (At that prompt, Frank quickly places a phone call to his "cat-eye guy.") Dennis, meanwhile, is thrilled to play the heroic Dayman, while Dee plays, confoundingly, "a princess who works at a coffee shop" that falls in love with the Dayman, despite constantly identifying him as a "little, tiny baby boy" in a song that leaves everyone disturbed. As for Frank, he readily signs on to play the role of the "troll" who allows the Nightman to attack the Dayman — who, as it turns out, is named Antonio, for reasons that are never revealed.

As the show approaches, disaster ensues, despite Charlie's constant, simmering rage and the very best efforts of the production's apparent (and lackadaisical) stage manager, Artemis (Artemis Pebdani). Right before the gang goes on stage, amidst Dee's insistence that she "rip the pits" of her ill-fitting yet expensive princess costume and Mac's announcement that he's trying to elicit "gasps" from the audience, Charlie makes a shocking proclamation: he won't be accompanying the show himself, instead giving his job to an elderly woman named Gladys and leaving the gang confused and stranded.

However, the real crux of "The Nightman Cometh" is that Charlie's musical, despite having some pretty catchy tunes — especially "Dayman" — is blatantly terrible, confusing, and utterly bizarre. Naturally, the gang makes all of that so much worse, between Frank's apparent inability to pronounce the word "soul" correctly, several dropped lines, a baffled audience made up mostly of senior citizens, and a backdrop and set of props that look like they were stolen directly from a terrible high school play.

Ultimately, Charlie's ruse is revealed as the show comes to an end. After "Dayman" closes the production, Charlie is lowered from the ceiling on an enormous sun in a bright yellow suit, singing a horrifying song that culminates in a proposal to his unrequited love, the Waitress (Day's real-life spouse Mary Elizabeth Ellis), whom he tricked into attending the show. Of course, she turns him down and exits — though Charlie assures her that he'll continue stalking her, as he does regularly — leaving Charlie embarrassed in front of the crowd.

"I told you nobody writes a musical for no reason," Dee says triumphantly as the gang takes their bows and leaves the stage, while Charlie and Frank, who live together, close out the episode with a tense, frustrated argument. All in all, "The Nightman Cometh" is definitely one of the very best episodes It's Always Sunny has to offer — and according to IMDb, fans agree. In fact, the episode remains so popular that the cast has performed the show live several times.

The first fourteen seasons of It's Always Sunny in Philadelphia, which has been renewed through season eighteen, are streaming on Hulu now.