Jennifer Lopez wore a backless red dress last night to celebrate her birthday in NYC with boyfriend Casper Smart, who matched in a burgundy sports coat. The couple went out in Manhattan and linked up with J Lo's manager, Benny Medina. Last year, Jennifer wore a bikini to ring in her 42nd year alongside Benny in Miami. Everything's different this year, though, since Jennifer has gotten serious with Casper. He's helped her celebrate the milestone with multiple meals out on the town this week. Yesterday was the big event — Jennifer was blindfolded and lead to a huge party on a boat, complete with a cake in the shape of a bear, which is Casper's nickname for her. She and Casper were seen dancing the night away on board, after her kids, Max and Emme, boarded the vessel earlier in the afternoon.