Limerick

Structure:

* Rhyme AABBA
* 5 Lines
* Lines 1,2,3,4,5 have syllables 8,8,5,6,8 respectively

Characteristics:
Humorous using absurd or dirty themes.

Origins:
Irish? It's not really known.
Example:

There was a Young Person of Smyrna
Whose grandmother threatened to burn her;
But she seized on the cat, and said, 'Granny, burn that!
You incongruous old woman of Smyrna!'

Lear