The third grade teacher was teaching English and repeated for her class, "Mary had a little lamb, whose fleece was white as snow, and everywhere that Mary went, the lamb was sure to go." She explained that this was an example of poetry, but could be changed to prose by changing the last line from "the lamb was sure to go" to "the lamb went with her."

A few days later she asked for an example of poetry or prose. Johnny raised his hand and recited, "Mary had a little pig, an ornery little runt, he stuck his nose in Mary's clothes, and smelled her little--"
He stopped and asked the teacher if she wanted poetry or prose.
"Prose!" the teacher said weakly.
So Johnny said, "a--hole".