Calling It's Always Sunny in Philadelphia a surprise success is an understatement. This show about the five worst people living in the city of brotherly love has become a tentpole of FX's programming, with 14 seasons in the tank. But the reality is that if Danny DeVito hadn't joined the cast at the beginning of Season 2, It's Always Sunny in Philadelphia would have ended years ago.
When the show launched in August 2005, it starred four main characters who had known each other for years. In some cases, their friendships had been going on since a very young age. Dennis Reynolds, Dee Reynolds, Ronald "Mac" McDonald and Charlie Kelly essentially formed a bond over being four terrible human beings who took selfishness to a whole new level.
But in Season 1, it was just the four of them. The gang was a bunch of goons who tried to screw each other over, along with anyone else possible. At the same time, they lacked the zany imagination that has typified their shenanigans over the years. As Jack Donaghy said to Liz Lemon in the first episode of 30 Rock, TGS needed that third heat to take the show over the top. Or in the case of It's Always Sunny in Philadelphia, a fifth heat.
In Season 2, Episode 1, Dennis and Sweet Dee were visited by their father, Frank Reynolds. Played by the legendary Danny DeVito, Frank was a successful and incredibly wealthy businessman. He was in the process of getting divorced and immediately sunk into the gutter with the gang. Frank would eventually work his way into their group, mostly by buying the land part of the bar was on and forcing his way in.
Frank Reynolds turned out to be exactly what the show needed. He facilitates many of the gang's plans with his vast fortune. As disturbing as this is, he is also the most depraved out of all of them. There are maybe a few horrific things he isn't capable of doing. In Season 9, Episode 4, he got himself trapped in a children's playground coil, dressed only in his underwear. While the official reason was never revealed, the gang assumes he went there to pleasure himself.
Frank offers a completely different perspective on the gang. There is a lot of history he isn't aware of. As such, the gang has to explain things to him frequently. Frank often represents the audience as he draws out the information viewers need to further understand the show and its characters. This came up in Season 7, Episode 7 as they had to explain Chardee MacDennis to Frank, a truly disturbing game they created years earlier.
The character of Frank Reynolds was the extra oomph It's Always Sunny in Philadelphia needed to get to the next level. He has been the catalyst for several stories that would not have existed without him. The depths of comedy the show has sunk to would not have been possible if Danny DeVito hadn't joined the cast. Simply put, Frank made the show's premise work -- and endure.