The facade of Paddy's Pub is apparently pretty popular
It's been shot in several other TV shows/movies/commercials, including one of my favorites Parks and Recreation. I noticed it right away while watching Parks but never bothered to do any research to see if it were the same location. Indeed it is, and someone beat me to it, so check out the comparison below along with some other instances of the great Paddy's Pub from It's Always Sunny. More at Uproxx.
Parks and Recreation at the top, actual view/Always Sunny at the bottom
Though no photographic evidence yet, apparently The Wire, Southland, and Mad Men have also filmed in front of Paddy's. Must be a stipulation for every FX show to incorporate the pub?