The Eldritch Quintuplets
There was a Mad Arab who said
That Cthulhu, though dreaming, is dead,
But some future night
When the stars become right,
He'll abandon his watery bed.
The Eldritch Quintuplets is the complete fictional works of HP Lovecraft, rewritten as limericks. I almost shudder to think what of Lovecraft's writing is nonfiction (his letters, probably. He basically starved to death while keeping up a huge correspondance. Very like a lot of bloggers ...) Of course, one of the assumptions in the 1970 nutcult classic Illuminatus! was that Lovecraft wrote only nonfiction ... Serious warning -- if you are offended by anything, it's in that book someplace.
I guess this one counts as both Harpo Marx and H. P. Lovecraft. "It's a floor wax! It's a dessert topping!"