st. pattyshit
When you are on the commode, drop a big one, and get up to look at it before whipping your ass (like everyone does), you notice that your shit has a green or greenish tint. This is usually caused by the consumption of a lot of green vegetables in proportion to anything else.
"Hey man, do you see that vegan over there? I bet he had to take a st. pattyshit this morning."