Haha, this post reminds me of the time my sister brought over a cake with blue embellishments on it, and all of my kids ate it..... and I forgot all about it until a few days later when all of my kids had crazy green poop. I thought they were all sick with some weird tropical virus or something. Pregnancy brain, you know. Anyway, plenty of other color dyes in your food could cause this. Of course, eating a lot of anything green. I think it's also caused by your food going through your digestive system too quickly and your body didn't get to process all the food and change it to brown before it passed. If it only happens once, I wouldn't worry at all. If it happens a few times, I'd call the dr.