Fecal eclipse 

When a person poops out a solid turd that is immediately followed by a stream of diarrhea, thus darkening the toilet water and obscuring the original turd from view. A fecal eclipse can be partial or total, depending upon the volume and opacity of the diarrhea. Because a mixture of solid and liquid shit is already rare, a total fecal eclipse where the view of the original turd is completely blighted from view is considered one of the rarest occurrences in the natural world and has long fascinated scientists and the casual observer alike. Throughout history, cultural interpretations of fecal eclipses have varied widely. For example, in China during the late Sung Dynasty, a fecal eclipse was thought to portend a favorable rice harvest in the upcoming growing season. In contrast, the ancient Egyptians, particularly during Egypt's Middle Kingdom period, believed that a fecal eclipse signaled that the annual Nile River flood would be too severe and wash away more of the nutrient-rich silt than it deposits, thus leading to a period of hunger and famine. In 19th century Ireland, a fecal eclipse was generally regarded as a sign of good luck for the person producing it, but with no broader implications for the rest of the community.

Tony: How as that poop?
John: I had this awesome long turd and I wanted to send you a pic, but then I had some diarrhea which caused a total fecal eclipse. Water was too cloudy to see anything.
Tony: Strange. I wonder what fortune this portends for you.

John: Don't be superstitious dude. It's a rare but completely natural phenomenon.

Fecal eclipse by Butt Pirate Roberts May 21, 2018