1. The Show Was Originally Going To Be Called Jerks
While the pilot was called It's Always Sunny On TV, the working title for the show was simple 'Jerks'. This is probably an apt description of the characters who are sociopathic, selfish and bordering on the insane (but loveable). The gang put the characters of Seinfeld to shame and the show was marketed by FX as being 'like Seinfeld on crack'. It is the anti-Friends: nobody learns their lessons and they just go out and do something just as, if not even more, deplorable the following week. Jerks might be a perfect description for the characters but it's hard to imagine the show being called anything other than It's Always Sunny In Philadelphia, which is instantly memorable and strikes up just the right amount of sarcasm. When developing the series the writers were reportedly offered $500 to come up with a title that the creators liked better but the title thankfully stayed.
