Part of the undeniable charm of "It’s Always Sunny in Philadelphia," even after 20 years on television, lies in its whimsical soundtrack — the satisfying irony of hearing rather pleasant tunes while watching the worst group of people wreak havoc across the city.

Die hard fans know that some of the best "Always Sunny" music comes from the show’s originals, whether it’s the legendary "The Nightman Cometh" musical or Charlie (Charlie Day)’s unexpectedly endearing “I Like Paddy’s Pub.”

But the soundtrack, composed of mostly free-to-use tunes, is the show’s special sauce, from cheery transitions to the series-defining theme song, titled (almost unbelievably) “Temptation Sensation.”

The bright waltz from German composer Heinz Kiessling has become synonymous with "Always Sunny," and Philadelphia as a whole: The Giants once notoriously played the track to troll the Eagles after a loss at MetLife Stadium in 2021, a move that would’ve enraged the Birds-loving "Sunny" gang. It’s become so popular that one bride used it to walk down the aisle.

Kiessling likely never imagined that his easy-listening compositions would later serve as introductions for episodes like “Mac Kills His Dad,” “Frank Sets Sweet Dee on Fire,” or “Who Pooped the Bed?” But his sweeping violins have become perfectly timed punchlines for the show’s cold opens, accompanied by the intro’s shaky video tour of local landmarks.

No matter how raunchy, violent, or silly the plot gets, the theme song remains absurdly positive, like a ray of sonic sunshine.

Fans have John Landgraf, then-president of entertainment and now chairman of FX, to thank for “Temptation Sensation” becoming the signature "Sunny" (and Philly) sound. The show initially had nothing to do with Philadelphia; they weren’t South Philly bar owners, they were Los Angeles actors. Rob Mac (formerly McElhenney), Day, and Glenn Howerton shopped their cheaply shot pilot to several networks, most of whom were unamused until Landgraf saw its potential as an anti-"Friends."

One of the few creative changes FX requested was nixing the entertainment industry premise because it was overplayed in other popular shows at the time, from "Curb Your Enthusiasm" to "Entourage."

“The network came to us and said, ‘We don’t want a show about actors,’ and we said, ‘Fine, let’s put it somewhere else,’” Mac told the New York Times in 2007. “I’m from Philly, let’s put it in Philly, and we’ll make it about a bar, because that’s a job where you can have lots of free time and still have income that could explain how these people can sustain themselves.”

"It’s Always Sunny on TV" became "It’s Always Sunny in Philadelphia" and the notorious South Philly gang was born. It was still a risk for FX, though, so the team operated on a shoestring budget — hence the need for public domain music. The theme song was going to be a version of “Hooray for Hollywood,” but they needed something new, so music supervisor Ray Espinola recommended Kiessling, among others.

“We said, ‘Give us everything you have in a sort of 'Leave It to Beaver' with a big band-swing kind of feel,’ and the majority of the songs are from what [Espinola] sent over,” Day told Entertainment Weekly in 2010. “When you set it against what these characters were doing — which often times can be perceived as quite despicable, or wrong — it really disarmed the audience. It just became our go-to library of songs.”

Still, “Temptation Sensation” wasn’t the guys’ first choice, it was Landgraf’s.

“We were leaning towards ‘Off Broadway’ [by fellow German composer and Kiessling collaborator Werner Tautz] to be the theme song,” Day continued. “But John Landgraf, the president of the network, really liked ‘Temptation Sensation’ and he put his foot down. Now I’m happy it’s the theme tune.”

Day agrees, though, that the name is funny. “Yeah, it’s much more a title for a pornographic film,” he added.

The 2010 album of "Sunny" songs is almost entirely written by Tautz and Kiessling. While tracks like “Off Broadway,” “On Your Bike,” and “Hotsy-Totsy” serve as unforgettable backdrops to the gang’s unhinged antics, they’re still available for use in other shows and commercials, leading to some unexpected connections in "SpongeBob SquarePants" and "RuPaul’s Drag Race."

“There was a year where ..., the 'Sunny' theme was the 'Madden' theme … [and] they’re using 'Sunny' music on 'Minecraft' videos,” Mac noted on the "Always Sunny" podcast in 2022. “You hear it in commercials all the time.”

“It used to upset me, because I’d be like, ‘Oh, man, dang it. Why didn’t we just, like, have a theme song that was just ours,’ you know?” said Howerton in the same episode. “But I think maybe it ended up working in our favor, because, like, every time those songs play, people think of 'Sunny.'”

It’s true that, after decades on air, there’s no separating these tracks from "Always Sunny" — no matter how much they’re used elsewhere. Managing to turn stock music into comedic gold is just one of the reasons we still love the show.

©2025 The Philadelphia Inquirer. Visit inquirer.com. Distributed by Tribune Content Agency, LLC.