If you happened upon a grimy, abandoned barrel sitting on the street, your first thoughts might run to, Ew, or even, How many spiders does that probably contain? In this very important way, you are different from deliriously privileged hipsters Harper (Bridey Elliott) and Allie (Clare McNulty), whom we follow in the new comedy Fort Tilden (out this Friday in New York). These two Brooklynites spy that street barrel and immediately respond to its “wear” — how authentic! — and start making an overpriced deal with the dude who just happens to be sitting next to it. Their hilariously blinkered perspective led our critic David Edelstein to call Fort Tilden a “cheerfully caustic comic odyssey,” even if satirizing hipsters is a little bit like shooting fish in a … well, you know.