The third season of It's Always Sunny in Philadelphia, premiered on FX on September 13, 2007. The season contains 15 episodes and concluded airing on November 15, 2007.
The gang finds a baby in a dumpster, and Dee and Mac decide to raise him. Meanwhile, Dennis wants to join a group of environmental activists and Charlie attempts to learn the truth about his paternity.
Mac, Dennis and Dee try out for the Philadelphia Eagles. Also interested in becoming an Eagle is Liam and Ryan McPoyle's brother, Doyle.
After Barbara's death, Dee and Frank are unhappy to learn that she left them both out of the will, while Dennis inherits the mansion which he plans to turn into a party pad.
The McPoyles hold the entire gang hostage at Paddy's; while Frank is busy searching for his will in the air ducts.
Dee is shocked to learn that an overweight social outcast from her High School has become a rich and skinny fashion designer.
A Korean restaurant owner threatens to get Paddy's kicked off the route for the city's annual pub crawl. The gang's response: War.
The gang agrees to sell Paddys when they get an offer that is too good to refuse, but it forces the bar's non-partners, Dee and Charlie to find new jobs.
Mac teams up with Frank and Charlie to create a public access newscast after he misses his chance at fame in the news. Meanwhile, Dennis and Dee try to make it big in the club scene.
Dee gets involved with a famous local rapper who might be mentally challenged, and whose success inspires the rest of the gang to start a band.
After Mac arrives to the bar with scratches on his neck and exhibiting strange behavior, Frank comes to the conclusion that he is the serial killer terrorizing young women in Philadelphia. Frank sets out with his trusty chainsaw and a doubtful Charlie to find evidence to implicate Mac in the murders. In search of another suspect, Dennis and Dee do a little role-playing in order to help themselves better understand who they might be dealing with.
When Dennis is mistaken for a recently released child molester, he is more bothered by the fact that the guy is overweight rather than him being a sex offender. Meanwhile, Mac tries once again to bond with his ex-con father, who shows an interest in Dee.
After stumbling upon a kilo of cocaine, the gang is forced to pay off a $25,000 debt to the mob. Mac becomes a mob informant, while Frank pimps out Dennis as an escort at the local country club. Charlie stumbles upon an opportunity to sell illegal narcotics.
While paying off their debt to the mob, Charlie and Dee try to find a way to make fake cocaine in order to fool them, while Dennis ranks in thousands of dollars being pimped out at the local country club. Mac realizes his position as a mob informant isn't being utilized to its full potential.
Mac and Dee become vigilantes in order to remove the homeless from their neighborhood, while Frank and Dennis impersonate police officers.
In the season finale, Charlie accidentally puts Paddy's up as a prize for a dance marathon, which prompts the gang to enter the competition in order to save their bar.