This reminded me of an old joke that probably can't be translated from English:
Q. Why did God make semen white and urine yellow?
A. So that men would know whether they're coming or going.
(Note: Women are fond of this joke because "to not know whether one is coming or going" is a standard expression meaning "to be ignorant, foolish, crazy".)
It's been said that "there are good limericks, and there are clean limericks, but there are no good, clean limericks." (I'm 90% sure that there must be at least one limerick with this same "coming/going" wordplay as above, but I can't think of it right now. )смешные истории в шуточных стишках