Thirty years ago, sitcoms featured moral families, powerful friendships, and heartfelt messages. Those television audiences would not have believed you if you told them that, by 2018, the longest running live-action comedy series of all time would be about five horrible bar owners slowly devolving into psychopaths, heartless slobs, and peddlers of a drink called Fight Milk.

And yet, here we are. Thirteen years after it debuted in 2005, the FX comedy series It’s Always Sunny in Philadelphia earned that title, thanks in part to the willingness of the show’s creators — Rob McElhenney, Charlie Day, and Glenn Howerton — to explore the truly dark side of comedy. Still, for as long as the show’s run, even its biggest fans know little about the show’s storied history. Until now…

1. While waiting tables, Rob McElhenney — the actor behind Mac — did a simple writing exercise where one man confronted another dying of cancer. That exercise turned into the pilot script, which the gang filmed for about $100 (mostly in their own apartments).

2. Because Rob McElhenney was a huge fan of HBO’s Game of Thrones, he invited the show’s producers, David Benioff,and D.B. Weiss, to write an episode of Sunny. It was called “Flowers for Charlie,” and spoofed the book Flowers of Algernon.

Rob McElhenney / Twitter

3. Similarly, Game of Thrones show runners offered the gang a trip to Westeros. “They asked us if we wanted to be in an episode,” Howerton said. “Basically they said ‘if you guys want to do the show, we’ll write something in there.’ We just never have time to do it.”

Game of Thrones / HBO

4. Even though the gang slams beers, downs shots, and squeezes alcohol out of sunscreen bottles, the actors never drink on set. “It’s bad for insurance,” Glenn Howerton said, and would put the show at risk.

It’s Always Sunny in Philadelphia / FX

5. Mac tacked on mass to better match his avatar, but Rob McElhenney cultivated 50 pounds in six months when he realized the characters on other shows got better looking with time. So, of course, he wanted to do the opposite. He got fat instead.

It’s Always Sunny in Philadelphia / FX

6. Russians tune into their own version of the show called It’s Always Sunny in Moscow, which similarly features the dregs of society running a bar called Philadelphia.

7. The gang filmed the show’s opening credits by driving around Philadelphia at night with a hand-held camera. Even after 13 seasons, that cheesy opening montage remained the same.

It’s Always Sunny in Philadelphia / FX

8. When their stuntman got snubbed for the Emmy in Outstanding Stunt Coordination for a Comedy Series, the gang wrote an episode in response: “The Gang Tries Desperately To Win An Award.” In it, the characters alter their bar to be more like one you’d see in a cheery, award-winning sitcom.

It’s Always Sunny in Philadelphia / FX

9. Like the characters they play, Rob and Kaitlin own a Philly bar! Take a trip to the iconic Market Street in Philly, and you can dine at Mac’s Tavern, a gastropub and sports bar with offerings like Mac’s Chili and Sweet Dee’s Turkey BLT.

10. Water threatened to drown the gang in the season 11 finale. To get the shots they needed, the crew weighed down Danny DeVito, but when cameras stopped rolling, he couldn’t swim to the surface. On-set divers rescued him from drowning.

11. If you watch the show through the ending credits, you’ll see a still acknowledging RCG Productions and hear some weird, garbled sounds. Those sounds are random lines recorded by the gang (one being “is a brown, is a brown, is a brown”) and played backward.

12. According to Glenn Howerton, before the gang chose Kaitlin Olson to play Sweet Dee, they’d picked Saturday Night Live’s Kristen Wiig to play the show’s most bird-like character.

13. When Kaitlin Olson ultimately signed on as Dee, McElhenney confessed he had no idea how to write a believable woman into the show. Olson told him to write her character like he’d write anyone else, so Sweet Dee became just as sour as the rest of the gang.

It’s Always Sunny in Philadelphia / FX

14. It’s not really the 1993 Range Rover that makes Dennis a sociopath and a Golden God. Glenn Howerton knew his character would devolve into total madness from the beginning but “just wasn’t ready to go all the way with it at first.”

15. Rob McElhenney’s character goes by Mac. Charlie Day’s character goes by Charlie. So why is Glenn Howerton’s character named Dennis? Simple: the actor wanted to distance himself from the character he knew would become so depraved.

16. The creepy, milk-drinking McPoyle family was based on a real-life McPoyle family Rob McElhenny knew growing up in Philly. Thankfully they weren’t as inbred in real life, but there were a lot of them, which McElhenny fleshed out into zany characters.

It’s Always Sunny in Philadelphia / FX

17. Celebrities don’t join the gang too often for guest appearances, but Guillermo Del Toro did in the episode “Maureen Ponderosa’s Wedding Massacre.” Few fans recognized the Oscar Award-winning director as Pappy McPoyle, patriarch of the very odd McPoyle family.

It’s Always Sunny in Philadelphia / FX

18. Charlie spent 12 seasons stalking The Waitress, but in real life, Charlie Day and Waitress actress Mary Elizabeth Ellis married (as did Rob McElhenny and Kaitlin Olson)! Glenn Howerton married Jill Latiano, the pharmacist he tried the D.E.N.N.I.S System on.

19. Meanwhile, the horrendously scarred, perpetually victimized, drug-addicted street urchin and former priest known as Rickety Cricket is pretty happy outside the show: he’s married to Bones star Emily Deschanel.

It’s Always Sunny in Philadelphia / FX

20. After season one, network executives told the gang they were headed for cancellation if they didn’t add a big name to the cast. They asked Danny DeVito to guest star for season 2, but, after several games of Nightcrawlers with Charlie, he became a beloved, full-time cast member!

It’s Always Sunny in Philadelphia / FX

21. Remember cute little Kevin Arnold — played by Fred Savage — from the hit late-’80s, early ’90s sitcom The Wonder Years? Savage directed and produced 19 episodes of Sunny.

IMDB

22. The catchy tunes in “The Nightman Cometh” didn’t just pop out of the Paddy’s Wagon. While he may be illiterate in the show, Charlie Day is a talented musician and, after surely downing a few jugs of Fight Milk, led the charge in writing all the show’s music.

It’s Always Sunny in Philadelphia / FX

23. It’s Always Sunny in Philadelphia may seem like a slow descent into random chaos, but the gang knows how the show will eventually end. Chances are, it won’t be with a character confessing his love for another at an airport terminal.