Never seen FX’s “It’s Always Sunny in Philadelphia“? As a sitcom set in a bar, it’s exactly like “Cheers”, except with less clever sexual tension, and more bed defecation, black jokes and cannibalism. Which translates into must-see cable TV, debuting for its 5th season tonight at 10. Sort of in the same way Baltimoreans reluctantly embraced “The Wire” as a tourism hook, the Greater Philadelphia Tourism Marketing Corporation has put together an Always Sunny-themed tour of the city with stops at the Italian Market, Palumbo Recreation Center and City Hall. What do those seemingly innocuous locations have to do with this s-bomb dropping, DeVitoized half-hour o’ crazy? Do your homework with past seasons on Hulu.