Burger King’s Halloween Whopper is making a few people see green

Social media has been abuzz recently about Burger King’s new black Halloween Whopper, but it’s not because of its burnt looking black buns.

Should all this poop talk inspire you to perform a science experiment of your very own, the Halloween Whopper is available in Burger King restaurants now through the end of the month. But the sandwich packs a spooky surprise: Eating it can turn your poop green.

There was no detectable A.1. flavor in the bun and just the slightest schmear of the sauce, which made one wonder why BK went to such great lengths to advertise their partnership with Kraft (owner of A.1.) on this venture.

But since we don’t have the ingredient list on hand, let’s review other possibilities: Green poop can also be caused by the presence of bile, which can show up if bowel movements move a little more quickly than usual through the intestinal tract.

“The dyes that make the bun black are a combination of Yellow #6, Red #40, Caramel Color, and Blue #1”, Gizmodo reported.

The black burger, sometimes called the Goth Burger by fans, has been a regular promotion at Burger King’s Japanese locations since 2013, however the USA version is formulated differently. It would definitely take a few tint tweaking to reach the desired effect, and a dark green seems as likely a dye color as any.

So why exactly is the poop turning green?

Burger King has not offered an official explanation for how the Halloween Whopper causes #greenpoop.