Limericks are 5 line Irish or English style poems with the same rhythm and beat in lines 1-2-5 and a shorter identical beat in lines 3-4. The rhyme pattern is usually AABBA, but many limericks suffer from near rhymes. They can have a variety of metrical feet such as amphibrach, 1 stressed syllable then 2 unstressed, or the inverse the anapest, 2 unstressed syllables then 1 stressed. These poems are usually humorous and memorable. The first line traditionally introduces a person. The second, third and fourth are the situational setup. The fifth line is the twist or comic punch line.
Example: by Frank G. Poe, Jr.
Lad from Washington, DC
There once was a lad in the government.
By the time he got paid it was spent.
Spending was all that he knew,
And the deficit grew.
In November out the door he went.