Burger King‘s new Halloween themed Whopper has a strange side effect after eaten, it’s turning customer’s stool green.

In what should have been a St. Patrick’s Day release, The Burger King Whopper sandwich, that features a black bun, is leaving some consumers confused and concerned after visiting the bathroom.

Looks appetizing enough, but, while it may leave a pleasant taste in your mouth, it seems to leave behind some unpleasant waste in the toilet. A quick visit to Twitter will tell you the black bun is turning people’s poop green. fox4news

People who consumed the scary burger are sounding off on social media using the hashtag #greenpoop. Burger King has yet to addressing the crappy by-product.