Sentence:  Why do they call camels "Ships-of-the-desert" ?<br />[...]<br />Because they're full of Iranian seamen.<br />(NOW, being <WSD>politically correct</WSD> you must, of course, substitute "martian"<br />What a clever joke this becomes! Hopefully, there are no martians listening. ) 
Meaning of the word marked with <WSD> tags:  Respectful of and avoiding offending certain genders, ethnicities, sexualities and/or other demographics.