PARK SLOPE Everyone talks about how kids today are all about the “hooking up,” but nothing beats those 70s key parties. In honor of Valentine’s Day, Southpaw is hosting a modified version of the swinger-friendly seventies game, where each guest will get a key with a tag for their phone number to drop off on the way in, and can grab someone else’s on the way out. Disco-friendly outfits are encouraged, and in return guests will receive an open beer and wine bar, a buffet of snacks, party favors, and music to dance to. Tickets are $20.