For those who don't read The Right Way by Jennifer Stewart, a fun/pun from her recent effort:
There was once a very smart horse. Anything it was shown, it mastered easily, until one day, its teachers tried to teach it about rectangular coordinates, and it couldn't understand them.

All the horse's acquaintances and friends tried to figure out what was the matter and couldn't. Then a new fellow looked at the problem and said, "Of course he can't do it. Why, you're putting Descartes before the horse!"
Grrroooooan !
(The louder they groan, the better they like it!)