At first, Welcome to the Johnsons seemed like nothing more than a great ironic joke. A theme bar for kids too cool for theme bars, it’s decked out just like your parents’ rec room circa 1978 — faux-wood-paneled walls, a vintage brown refrigerator, sports-league trophies, even a Ms. Pac-Man game. But unlike certain other irony-tinged nightspots, there’s lots here to keep you coming back even after the wink-wink factor has worn off. Drinks are dirt cheap, including (during the summer) first-rate margaritas as potent as the ones you used to sneak from Dad’s basement liquor cabinet. And the crowd, still mostly locals, is filled with more than enough hipster cuties to make you want to start a round of spin-the-bottle.