HALLOWEEN COSTUMES: COUPLE COSTUME: DON JON AND BARBARA 'Don Jon' stars Joseph Gordon-Levitt and Scarlett Johansson played one hot couple on screen. For you: Shimmy in a body-hugging red-hot dress with gold hoops. For him: Show off those guns in a sleeveless vest (don’t forget to have your guy slick back his hair). Dress: Mango, $80; mango.com. Earrings: Bebe, $22; bebe.com.