Longtime fast food chain Burger King launched its black-bunned theme burger last week just in time for Halloween.
But customers on social media have been reporting back about the Whopper of a surprise that follows after consumption.
Suffice to say, when your body processes the bun it plays a strange trick on your body - and what was black turns a ghastly shade of green when it comes out the other end.
Yet kudos to BK. As far as marketing ploys go, this one will no doubt see sales boom faster than you can say "boo."
Although some people are clearly revolted at the prospect of eating a burger that turns your poop green, curiosity will get the better of many others eager to try out the gross experiment.
And if you do happen to munch the Halloween burger, don't fret.
BK claims its black bun "contains less than one percent food dye" and falls well within industry standards approved by the Food and Drug Administration (FDA). And inquiring minds will want to note that green dyes are often used in black food colouring.
Something tells me this is one science project my husband and son will be only to willing to try at home.