There once was a master sculptor who prospered in a strict, but respected art school. He was excellent in his craft, quickly surpassing the skill of his master and that of his fellow pupils. However, he was too good at his trade, and grew bored after just a few sculptures. They were masterpieces, each perfectly designed and executed, but to the sculptor, they were just plain and simple. He wanted something more, something new, something different. He started to experiment with new techniques and different substances, but was discouraged from doing so by his envious artistic peers. He had still been able to make masterpieces, unlike any the world had known before. However, in doing so, he had violated many art laws, which his peers took very seriously. But he didn't listen to them, so they destroyed his statues and exiled him. Then they brought him to a manhole which lead to a sewer and said, "Here is your new workspace! Let's see you work with this!" And they threw him in.
The sculptor looked around. They had sealed him inside the sewer. What was he going to do? He couldn't live here. Covered in grime and sludge and muck, he realized that he would die here, dirty, alone, and unappreciated. Determined to make one last sculpture, he needed a subject. "I'm going to die here," he thought. "So I might as well leave a record of my existence." And so the sculptor decided upon a subject: himself. Now all he needed was a material, but what was there down here that he could use? Looking at his filthy hands, he figured it would be useless trying to stay clean, so he looked around to see a potential material with which to sculpt.
Splat, splish, splash.
The sculptor turned toward this curious noise. It was human excrement. He was in a sanitary sewer. As this was the only thing there, he began to collect it and sculpt. He found that it was actually the best substance he had ever worked with. The sculptor worked for hours on end, without food or water, and finished his self-sculpture, and signed it, proving his existence. However, he collapsed of exhaustion in the process. Laying in the waste of what quite possibly could be that of his former art peers', he died, longing to work more with this newly discovered substance.
It is said that his ghost still wanders the sewers of the world, traveling through sewage pipes to collect the materials that he so desires. However, out of his hatred for his jealous art peers, he creates only the most horrific-looking sculptures. He will go so far to gather excrement that he will go to your very own toilet, the moment you sit down, sticking his hand just under your bottom with a bag to collect your bowel movements. If you try to look at it, it will disappear before you are able to notice it, and if you get constipated and make him impatient, he will remove your bowels for you. However, if he still does not extract them, he will drag you through the sewers to his workplace, where he will show you his terrible sculptures. They'll scare the shit out of you.