On a side note, i think it was either an episode of Criminal Minds or Law & Order were some kid killed two thugs that were trying to mug him and it was on the same "strip" as Paddy's. Since I can't remember where the episode took place I'm wondering, is that strip really in Philly or is it in L.A.? I always figured It's Always Sunny was filmed in Philly.
IIRC, the show is predominantly filmed in LA, but they'll go to Philly to do location shoots when they need to. Law and Order, of course, is filmed in New York, so there wouldn't be any LA shots or Philly shots in it.