ON LIMERICKS

A Limerick is a short poem (5 rhyming lines : aa bb a) Lines 3 and 4 always a maximum of 3 (sometimes 2) stressed syllables. The last line generally sounds like a big surprise.

There was a young girl from St Paul

Wore a newspaper dress to a ball;

But the dress caught on fire

And burnt her entire

Front page, sporting section and all. 

Most of the time, the end is absurd, so this form of poetry is often classified as nonsense (a bit like Lewis Carroll's Alice in Wonderland). Edward Lear is the most famous limerick writer, but limericks can be anonymous.

There was a young lady of Riga,

Who smiled as she rode on a tiger;

They returned from the ride

With the lady inside,

And the smile on the face of the tiger.

Sometimes they start from funny situations : 

A traveller when dining in Crewe
Found a fat little mouse in his stew.
Said the waiter, "Don't shout
And wave it about,
Or the rest will be wanting one, too"

Or they can be pure phonetic games:

 There was a young fellow from Bicester

Who fell in love with his sicester

When accused of incest

He lost interest

But he still got a thrill when he Kicester

You'll find a lot more on the Internet (quite a ... serious one http://www.thehypertexts.com/The%20Best%20Limericks%20of%20All%20Time.)