A rhyme about telling a story that turns out to be the whole story: Jack-a-Nory and his brother each get a sentence before it's over. A small joke about how tales get spun out, and a neat closer for a rhyme session.
From Mother Goose / Nursery Rhymes (traditional). See the whole collection.
I'll tell you a story
About Jack-a-Nory:
And now my story's begun.
I'll tell you another
About his brother:
And now my story is done.
Public domain. Text from The Real Mother Goose (Blanche Fisher Wright, 1916), via Project Gutenberg. View the source edition