Burger King (BKW) is gearing up for Halloween in spooky style with a new Whopper sandwich. The Halloween whopper comes with a black bun, which has the A1 smokey steak sauce baked in. A similar burger went on sale in Japan last year, which also included black cheese and derived its color from Squid ink and bamboo charcoal. The murky looking treat from the world's number 2 hamburger chain has received mixed reviews from customers so far. It goes on sale at $4.99 and will be available for a limited time only.