Limericks are fun, aren't they, children? And they're easy to write too. There are five lines in a limerick, with the first, second and last lines rhyming with each other, and the third and fourth lines rhyming with each other as well. There's a simple 3, 3, 2, 2, 3 syllable pattern as well.
Limericks were a great source of fun in the long-ago days when there were no Playstations, and there was relatively little to do apart from chew stalks of grass, milk a cow or fiddle with one's testicles. Folks would make them up about anything, and this became very popular, especially amongst the lower classes, who generally had bigger and more hairy testicles.
In Ireland, limericks became so popular, that a town named itself after limericks, and the town of Limerick still bears the name today. The inhabitants all had potatoes growing out of their ears, the filthy bastards.
Here's a limerick I wrote earlier to show you all how piss-easy it is:
There was an old man from Bangkok
By whose routine you could set your clock
He rose early at seven
Retired at eleven
And till midnight he played with his cock.
Why don't you have a go, you waster?