Danny DeVito’s involvement in It’s Always Sunny in Philadelphia was the result of a network stipulation. Creators and co-stars Glenn Howerton and Rob McElhenney had impressed FX with a short film that was the show’s pilot back in 2005, but low ratings for the first season demanded a change up within the cast. It was a necessity to keep the show on air, but Howerton, McElhenney, Charlie Day, and Kaitlin Olson had already developed a dynamic thanks to their existing friendships. The inclusion of an A-list star to boost ratings was tantamount to “selling out,” but it was the only option to keep an unusual, satirical dark comedy on the air.
The introduction of DeVito as Frank Reynolds, an absentee father to Dennis (Howerton) and Dee (Olson), as well as the roommate to Charlie (Day), was seamless. It’s easy to forget that DeVito wasn’t just an 1980s star in need of work, but an accomplished filmmaker; as an Oscar-nominated producer and director of dark comedies like The War of the Roses and Throw Momma From The Train, DeVito had shown expertise. Even if DeVito’s films weren’t cited as a direct influence on It’s Always Sunny in Philadelphia, it’s not hard to see that they share the same DNA. Howerton and McElhenney weren’t the first actors with filmmaking ambition that DeVito had supported; he also produced Ben Stiller’s Reality Bites, Zach Braff’s Garden State, and gave Jim Carrey the platform to become Andy Kaufman in Man on the Moon.
The most subversive aspect of DeVito’s involvement in It’s Always Sunny in Philadelphia wasn’t that he was cast as a narcissistic sociopath, since he’d pulled off equally despicable roles in Batman Returns and L.A. Confidential. The gimmick was that this was the first time that DeVito had played a low-status bottom-feeder. He’s previously been the embodiment of gross wealth and pretentious apathy, cast to play an egocentric movie star in Get Shorty, a haughty fashion tycoon in Ruthless People, and a sleazy salesman in Tin Men. Frank’s a fascinating character because of how ridiculous it is to imagine that he’s survived for this long. He’s so feckless that his children refer to him by his first name, and so careless that he’s destroyed the lives of many guest characters throughout the show’s 21 years on the air. That DeVito is thought of as an underdog gave because of his short stature, the result of a rare genetic bone disorder, allowed It’s Always Sunny in Philadelphia to have him voice the offensive, irregular, and psychopathic lines that the regular cast could have gotten away with.
The reason that It’s Always Sunny in Philadelphia became the longest-running live-action sitcom (a title it took from The Adventures of Ozzie and Harriet in December 2021) is that it's cyclical. These are selfish characters who haven’t become any smarter or more mature, even if the world around them has gone through an identity crisis. It’s Always Sunny in Philadelphia began the same year that YouTube was launched and three years before the financial collapse, and that it’s spanned the course of four presidents. These cultural shifts have forced the show to think about how it is framed; there was a notable rejection of the lionization of popular culture during the Obama era, as well as allusions to more progressive sentiments in the first Trump administration. Now, the It’s Always Sunny in Philadelphia characters could be claimed by those from all across the political spectrum, and have a barrier to empathy that has eluded them from consequences.
The 17th season of It’s Always Sunny in Philadelphia marked an instance of acknowledgement to the guest stars, running gags, and unresolved tension. It was a necessary moment of self-awareness needed to prevent the series from going through the motions, but the 18th season is a corrective return to form. The season 18 premiere “Frank Marries A Corpse” teased a happy future for Frank before his bride-to-be Samantha (played by DeVito’s former Taxi co-star, Carol Kane) is killed by flesh-eating bacteria. It’s not a tragedy for Frank, who discovered too late that she wasn’t in fact the heir to a fortune; even if DeVito has played the character as being vaguely sentimental, he’s still an opportunist.
The mindset of the It’s Always Sunny in Philadelphia characters isn’t linked to a specific era, but they’re intended to be isolated enough from the mainstream that anything new is to be treated with skepticism. There’re a few great gags in the new season that play into this; “The Gang Gets Tested” has Frank opposed to the infantilization of college campuses, and "2026: A Virtual Insanity" is a satire of the predatory tactics of concert vendors.
It’s Always Sunny in Philadelphia hasn’t yet been renewed for Season 19, but it’s hard to imagine that FX would pull the plug, especially given the extended episode count of the current season. In all likelihood, the show would have to be put to rest upon DeVito’s death. He wasn’t supposed to be part of It’s Always Sunny in Philadelphia, but it couldn’t go on without him.