Customers Claim Burger King’s Halloween Whopper Causing Green Poop........ MIAMI (CBSMiami) — Have you taken on a walk on the dark side yet with Burger King’s A1 Halloween Whopper? If you have, you may have noticed that while the seasonal black-bunned burger goes in one color, it may come out another. According to some folks who have downed the black-colored bun, there is an unexpected side effect, they’re passing green poop after eating their meal. Social media is lighting up with folks using the hashtag #greenpoop. The Miami-based chain unveiled the Halloween Whopper last month and said the bun’s black color comes from the A1 steak sauce. A Burger King representative said the bun contains less than 1-percent food dye, and the dyes “are commonly used in the industry and approved by the Food and Drug Administration.” The company did not state whether the bun contains Green #3, a food dye known to cause green-colored stool. CBSMiami.com has requested a statement from Burger King and we are waiting an official company response. In the meantime, #GreenPoop is trending and the company is certainly getting a lot of publicity.