Burger King has been selling a Whopper with a black bun for years in other countries, and people asked them to bring it to America. So they finally caved and introduced it as a special Halloween burger this year.

Well, maybe we should've left it in Asia.

(Burger King / Twitter)

Some people are finding there's a weird side effect of the black bun on the Halloween Whopper, it's turning their poop green. People are complaining on Twitter and even sharing photos of their green poop. We accidentally looked at one and would strongly advise you do not.

The ingredients for the bun include A1 steak sauce and four different food colorings, so somehow they're teaming up to have this side effect for some people. Fortunately there's almost no chance the green poop is a sign of any real health problems. Once the bun is out of your system you'll be back to nice traditional brown feces again.

Read more at Gawker.