When snorting coke off a toilet seat in a certain popular Sydney nightclub, some coke may drop and plop inside (unaccompanied or not by bodily emissions). The process of fishing it out is known as The Sydney Submarine
When you smoke weed out of your asshole, lighting and inhaling the weed through your asshole, while a girl sucks you off and you exhale the smoke through your penis, so she can therefore get high as well.