World Peace promoted by Burger King and McDonalds: ‘McWhopper’ : In honor of Peace Day, September 21st, Burger King is calling for a ceasefire with McDonald’s. We’re inviting them to work with us to create the McWhopper, a combination of our respective signature sandwiches. If they say yes, this peace loving burger will be available for one day at a pop-up McWhopper shop in Atlanta, Georgia on Peace Day.