Fiddler's Green is a character in the Sandman series by Neil Gaiman. Sandman is a fantastical, very intelligent and erudite story, or rather, series of stories, that draws on mythology and folklore and symbols from a diverse range of cultures and sub-cultures, and therefore the Fiddler's Green depicted in the series is both an intelligent, self-aware being and a place - an anthropomorphic personification who is the embodiment of the peaceful sailors' paradise and all it represents in the human psyche.
Fiddler's Green exists in the Dreaming, a realm governed by Morpheus, the lord of dreams and stories - in fact, leaving aside the castle of Morpheus himself, it is the heart of the Dreaming, the tranquil center around which all the chaos and change inherent in dreams revolves. If one can think of the Dreaming as a graphic representation of the collective unconscious, then it would be the archetype of earthly paradise. Morpheus himself likes to take walks through Fiddler's Green, especially if he's courting at the time.
In book two of Sandman, The Doll's House, Morpheus discovers that Fiddler's Green has left the Dreaming and is nowhere to be found, and we quickly find out that he is walking the waking world in search of experience and change, rediscovering the joy of human interaction and unpredictability. He has taken the form of a huge, fat man who apparently looks exactly like G. K. Chesterton, and calls himself Gilbert. Aside from being weird and saying "Hoom!" a lot, just like the ents in The Lord of the Rings, he seems to have no immediate relevance to the plot of The Doll's House until he saves Rose Walker's life twice: once when she's being attacked by thugs in a dark alleyway, and once by writing Morpheus' name on a piece of paper for her. Later, when Rose is being attacked by a serial killer calling himself Fun Land, she grabs the paper and whispers the name, and he appears to save her.
Fiddler's Green returns to the Dreaming of his own accord, and Morpheus doesn't have the heart to punish him for leaving, perhaps because he had good intentions and did no harm. He tries to save Rose Walker's life one more time by offering his life for hers to Morpheus, but the Dream Lord refuses to accept the bargain. Does Morpheus end up killing Rose? Better buy the book and read it. Sorry.
He makes a cameo appearance in Book six, Fables and Reflections, in a story called Soft Places, when he meets Marco Polo in a desert at the edges of the Dreaming. Marco has stumbled into this place by accident - it's a shifting zone, where dreams and reality are blurred. Time has no real meaning there, and people who enter the shifting zones cannot usually return to the waking world. Fiddler's Green sits with Marco and his companion Rustichello at a campfire for a while and tells them stories they don't fully understand. At some point a band of lost warriors ride up to them - they've been stuck in the shifting zones for a long time, and are looking for a way out, but he can't help them:
Warrior: Sir? If we ever returned to the Hard Lands, there are some amongst us who believe that we would die of old age, crumblind to dust like the men in the tales. Others claim that we would return to the world on the day we left it, and live out the span of our lives -- And all the time we spent in this place would fade and vanish, like a dawn dream on waking that colors the day but cannot be touched or remembered. Which would it be, sir? Which would it be?
Fiddler's Green: I wish I knew.
Warrior: Aye. So do we, lord.
Fiddler's Green is killed in Book nine, The Kindly Ones, by the Furies, who are systematically destroying Morpheus' realm. He dies in his humanoid form, with dignity and slight disappointment, cleaning his glasses distractedly and mourning the fact that his death had to be so meaningless and violent. Being an embodied dream, he is not fully dead, just as he was never fully alive, and in Book ten, The Wake, the new Dream Lord, in the course of his repairs to the damage done to the Dreaming by the Furies, attempts to resurrect him. However, Fiddler's Green persuades Dream not to do this, saying:
If you bring me back to life, my death will have no meaning. I had a fine existence. I was a good place. I spent a little time in the waking world. I even fell in love, once, a little. I lived a good life and it ended. Would you take that away from me?
Dream ponders a moment, and then lets him go.