The text of Walden from Project Gutenberg.
Much critical fuss is made about the "loon" passage.*
As I was paddling along the north shore one very calm October afternoon, for such days especially they settle on to the lakes, like the milkweed down, having looked in vain over the pond for a loon, suddenly one, sailing out from the shore toward the middle a few rods in front of me, set up his wild laugh and betrayed himself. I pursued with a paddle and he dived, but when he came up I was nearer than before. He dived again, but I miscalculated the direction he would take, and we were fifty rods apart when he came to the surface this time, for I had helped to widen the interval; and again he laughed long and loud, and with more reason than before. He manoeuvred so cunningly that I could not get within half a dozen rods of him. Each time, when he came to the surface, turning his head this way and that, he cooly surveyed the water and the land, and apparently chose his course so that he might come up where there was the widest expanse of water and at the greatest distance from the boat. It was surprising how quickly he made up his mind and put his resolve into execution. He led me at once to the widest part of the pond, and could not be driven from it. While he was thinking one thing in his brain, I was endeavoring to divine his thought in mine. It was a pretty game, played on the smooth surface of the pond, a man against a loon. Suddenly your adversary's checker disappears beneath the board, and the problem is to place yours nearest to where his will appear again. Sometimes he would come up unexpectedly on the opposite side of me, having apparently passed directly under the boat. So long-winded was he and so unweariable, that when he had swum farthest he would immediately plunge again, nevertheless; and then no wit could divine where in the deep pond, beneath the smooth surface, he might be speeding his way like a fish, for he had time and ability to visit the bottom of the pond in its deepest part. It is said that loons have been caught in the New York lakes eighty feet beneath the surface, with hooks set for trout—though Walden is deeper than that. How surprised must the fishes be to see this ungainly visitor from another sphere speeding his way amid their schools! Yet he appeared to know his course as surely under water as on the surface, and swam much faster there. Once or twice I saw a ripple where he approached the surface, just put his head out to reconnoitre, and instantly dived again. I found that it was as well for me to rest on my oars and wait his reappearing as to endeavor to calculate where he would rise; for again and again, when I was straining my eyes over the surface one way, I would suddenly be startled by his unearthly laugh behind me. But why, after displaying so much cunning, did he invariably betray himself the moment he came up by that loud laugh? Did not his white breast enough betray him? He was indeed a silly loon, I thought. I could commonly hear the splash of the water when he came up, and so also detected him. But after an hour he seemed as fresh as ever, dived as willingly, and swam yet farther than at first. It was surprising to see how serenely he sailed off with unruffled breast when he came to the surface, doing all the work with his webbed feet beneath. His usual note was this demoniac laughter, yet somewhat like that of a water-fowl; but occasionally, when he had balked me most successfully and come up a long way off, he uttered a long-drawn unearthly howl, probably more like that of a wolf than any bird; as when a beast puts his muzzle to the ground and deliberately howls. This was his looning—perhaps the wildest sound that is ever heard here, making the woods ring far and wide. I concluded that he laughed in derision of my efforts, confident of his own resources. Though the sky was by this time overcast, the pond was so smooth that I could see where he broke the surface when I did not hear him. His white breast, the stillness of the air, and the smoothness of the water were all against him. At length having come up fifty rods off, he uttered one of those prolonged howls, as if calling on the god of loons to aid him, and immediately there came a wind from the east and rippled the surface, and filled the whole air with misty rain, and I was impressed as if it were the prayer of the loon answered, and his god was angry with me; and so I left him disappearing far away on the tumultuous surface.Like the tortoise in The Grapes of Wrath, the loon is known to be highly symbolic and Cliff-notable. For instance, I read on Yahoo's homework help site (who knew?) that "In the loon, the integration of the animal and the spiritual is also seen. The loon in Walden Pond is certainly wild, and that he is more than merely wild is revealed by the narrator's word choices." To think people actually hate English class! All right; I sort of see the integration of the spiritual and the animal, although none of these words have any meaning. And yes, the loon is "more than merely wild."
What I'm interested in here is not the loon as a symbol (god help us) of wildness, but a definition of it. In other words, the loon does not represent wildness, he is wildness itself. And by "wildness" I don't just mean nature vs. human, but complete otherness. The loon is a complete outlier, not just to Thoreau, but to the everyday life of the pond--his "looning" is the "wildest sound that is ever heard here." He makes the woods ring. He's in complete command of the place for the time he's there. He cannot be caught, but he also doesn't really belong there in the first place. All this makes him the very opposite of a symbol, because he can't be interpreted. He eludes and resists--that's what he does, and is.
I'm fascinated by these kinds of uninterpretable figures in literature. Bartleby the Scrivener, whom I have a feeling we'll be talking about soon, is another one. He's simply there, inscrutable, which drives his boss, the narrator, crazy.
A fun exercise (yes, we're there at last) would be, I think, to create a similar type of figure--a kind of fascinating and impenetrable visitor, human or otherwise. This being can be the center of the story--and may inevitably turn out to be that--or a sort of thread that runs through it, popping up at strange times.
Oh--and no, you can't have Bigfoot; he's mine. But here are some other possibilities:
--Some non-copyright-violating version of the Joker from The Dark Knight. Not necessarily evil, though.
--Mini black holes created by the Large Hadron Collider
--Mark "The Bird" Fidrych
*Possibly revealing note: doing a search for "loon" in Walden, I get the following results: pantaloons (at least thrice), balloon, and saloon--along, of course, with just plain loon.