Limericks are often humorous or even obscene. "As limericks were short, relatively easy to compose and bawdy or sexual in nature, they were often repeated by beggars or the working class in British pubs and taverns of the fifteenth, sixteenth and seventeenth centuries." The word limerick derives from the town of Limerick, Ireland and the pub song "Will you come down to Limerick?" where such a song was sung (http://www.famousliteraryworks.com/limericks.htm).
Here is one of Edward Lear's poems:
There was a young lady from Niger
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.
The first American limerick appeared in the Princeton Tiger:
There once was a man from Nantucket
Who kept all of his cash in a bucket.
But his daughter named Nan
Ran away with a man
And as for the bucket Nantucket.
Here is a more modern limerick:
New York is a fabulous place
Where everyone gets in your face.
English ain't spoken
Unless it is broken
And nothing is said lowercase.
Here is my first attempt at a limerick from several summers ago:
A peach and a pear set to wed.
For they were in love it is said.
Cried the peach: "Let's elope!"
Asked the pear: "How will they cope?"
So the peach married a nectarine instead.
For more information on how to write a limerick, visit http://www.wikihow.com/Write-a-Limerick.