With over 10 seasons on the books, It's Always Sunny in Philadelphia, has established itself as one of the mainstays of modern comedy. Over those double digit seasons, IASiP has some of the funniest and lasting running gags and running jokes on television.
Take for instance Charlie's illiteracy; it could have easily been a one-off joke, but the gang has stretched it over the course of every season, and it's still as funny now as it was the first time it came up. There are plenty more running gags from the Sunny writers where that came from, so take a moment to vote up your favorite It's Always Sunny running jokes below!
Dennis Being a Sociopath
Charlie and Bird Law
Rickety Cricket's Spiral Into Ever-Greater Horrors