As one studies the history of It's Always Sunny In Philadelphia, it becomes clear that each of the show's main characters have regressed as human beings over the course of seven seasons. Dennis has become more vain, Dee more conniving, Mac more reckless and Charlie has shaved off about 30 IQ points. But none of the show's principles have dropped in morality, behavior and basic hygiene in quite the same manner as Frank Reynolds (Danny DeVito). When introduced at the beginning of season 2, Frank was a successful, if shady, businessman. His appearance was tidy and his behavior was reasonable. In the time since he's joined the gang, his vices have gone from gambling on children's basketball and running Russian roulette games to invading homes and eating cake mix (while in a dog cage). The only thing more shocking than Frank's character arc is how consistently it descends from season to season. Join us in examining twelve defining moments of Frank Reynolds devolution, from wealthy entrepreneur to Rum Ham-enjoying bed pooper.

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Charlie Gets Crippled

Frank makes his first appearance, and promptly tells his children, Dennis and Dee, that their mother is dead. He then admits that their mom is only divorcing him, and the death hoax was his way of softening the blow. Frank decides to remake his life as "part of the gang," hanging out at stripclubs with Mac and Charlie and even moving into Charlie's disgusting apartment.

Dennis and Dee Get a New Dad

When Frank learns that the children he had raised as his own were fathered by another man, he goes off the deep end. He also suffers a mild stroke, which could explain some of his behavior in recent years. This episode also features Frank recklessly firing a gun indoors, something which would become a hilarious staple of seasons to come.

Dennis and Dee's Mom is Dead

Frank once again tells Dennis and Dee that their mother is dead, only this time it's the truth. Any normal person would be saddened or at least shocked, but Frank is so elated by the news that he pops open a bottle of Champagne. Later, his joy crashes hard as learns his dead ex-wife has left most of his fortune to her former lover (and the biological father of the twins). Frank launches a con in order to get the money back, which leads him to almost marry Dee, the woman he raised as his daughter. He really wanted that money.

Who Pooped the Bed?

Did I mention that Frank, a wealthy businessman, has been sharing a futon with Charlie for several years? Well, he has. And when one of the two poops on that futon, it sets off a firestorm of accusation and investigation involving the whole gang. That is, until Frank cheerfully announces that he pooped the bed. Twice. And twice on the floor of the bar. He defends his actions, explaining that "poop is funny." And he's right, damn it.

Sweet Dee Has a Heart Attack

This episode opens with a shot of Frank taking a giant bong hit, reminding us how far he's come. It continues with the image of Frank's bare ass in a hospital gown, and the revelation that he cancelled his children's health insurance when they were nine. After ingesting a multitude of anti-anxiety pills, Frank wanders the streets and is committed to a mental institution. He stages a breakout (in an homage to One Flew Over the Cuckoo's Nest, which featured a young DeVito) and marches off to freedom... and more weed.

The Always Sunny Christmas Special

Dennis and Dee attempt to teach Frank a lesson as revenge for years of lousy Christmas presents. Of course, nobody really learns or evolves, but we do get the incredible sight of Frank tearing his way out of the inside of a couch at an office Christmas party. He is of course, completely naked. The visual will haunt you, but you will be unable to look away.

The Gang Gives Frank an Intervention

This Always Sunny classic is one of the few times the series acknowledged just how much Frank had changed, and as a result, the gang plans and intervention. This solves nothing, but we do get to see Frank hit on his newly widowed sister-in-law, and failing that, try to bang his niece. He rationalizes it by the fact that they aren't blood related. Frank also demonstrates a touch of his former inventive spirit, pouring wine into a cola can for added convenience. The episode features a Frank quote that pretty much sums up everything: "I don't know how many years on this Earth I got left... I'm gonna get real weird with it."

The Gang Wrestles For The Troops

When Paddy's Pub decides to organize a wrestling match to welcome home returning U.S. soldiers, Frank invents a wrestling persona called "The Trashman." This consists of Frank eating actual garbage, and then attacking his opponent with a trash can. This is all fun and games until Frank seriously injures the long suffering Cricket, nearly killing him. Still though, he won the match, and the troops all seemed to have a pretty good time.

The D.E.N.N.I.S. System

The D.E.N.N.I.S. System is the name of Dennis' plan for seducing and abandoning women. This has little to do with Frank, until it is revealed that Mac picks up these now vulnerable women where Dennis left off, and then Frank swoops in for "the scraps." This episode also features Frank in his persona of Dr. Mantis Toboggan, M.D., when he (falsely) informs Dennis that he has "got the AIDS- big time!"

Mac's Mom Burns Her House Down

Frank is afraid his children will eventually leave him in an old age home, so he attempts to show what a good father he is by caring for a sick Dee so she'll be able to attend a concert. Only he decides to drug Dee with extra cough medicine, thinking that it'll make her dependant on him. And then she falls down some stairs. The moral of the story is that Frank is a terrible father.

Frank's Pretty Woman

The current season of Sunny continued Frank's fall from grace, as he decides to propose to a hooker named Roxy. This leads to the gang scrambling to find him a date, and the revelation that, as disgusting as he's gotten, Frank likes who he is, and he's not hurting anyone, so other people should let him be. And then the hooker dies, of course.

Frank Reynold's Little Beauties

Frank may not have bottomed out yet, but he came damn close in this recent episode. Frank drunkenly buys into a beauty pageant, and then sobers up in time to learn it features children. He then spends the rest of the episode desperately trying to convince people that he isn't a "diddler." This was a man who ran his own company only six years previous. Despite all this, Frank remains probably the second most likable character on the show. We can only imagine where his adventures will take him next!

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Also check out Before They Joined The Gang, a look back at the Always Sunny Cast.