A Farkism for "When the S*** hits the fan", achieving noteriety in the thread What would happen if I were to boil some Poison Ivy leaves, and drink it like tea.?
When one of the farkers posted this from Usenet:
“The poison ivy oil (urushiol) wouldn't cause trouble in his throat, as a combining of that oil and the outer layer of the skin is necessary to form a complete antigen (allergen). He's likely to have trouble, however, when the oil hits his anus.”
the phrase “He's likely to have trouble, however, when the oil hits his anus.” caught on like wildfire, and is used whenever someone posts doing something that is considered dangerous, stupid, or just pants-on-head retarded, and is seemingly oblivious to the consequences of their actions.
This also spawned a spate of photoshops using this phrase or a variant of it.