"The Tooth Fairy Tats 2000" is the first episode of Season Four, and the 49th overall episode of South Park. It aired on April 5, 2000.
When Cartman discovers the Tooth Fairy is paying a premium price for his lost teeth, he and the boys seize the opportunity to make some cash. They act as entrepreneurs, and build a thriving business by appropriating teeth from the less fortunate. When the boys attempt to expand their racket, they come face-to-face with Denver's mob boss in the black-market tooth trade!
The tooth fairy has visited Cartman, leaving him $2. He rushes to the bus stop to share his news with the others and unveils his latest plan. If they all combined their lost teeth, the tooth fairy will provide them with enough cash to purchase a Sega Dreamcast. However, Stan and Kyle have lost all their baby teeth, but not Kenny. Cartman tries to get teeth out of his mouth by having Timmy pull one out with a string tied to his wheel chair, but it turns out Butters has a loose tooth, and is waiting for the tooth fairy. Cartman decides to steal Butters' tooth instead. Disguised as the tooth fairy, he steals Butters' tooth, and places it under his own pillow to get money. His mother gets worried about the number of teeth he has lost, and calls the local dentist, Dr. Roberts. She decides to come clean with Cartman, and admits that there is no tooth fairy. When Cartman tells the others, Kyle begins to question his own existence, while Stan decides that they can still get money for a Sega Dreamcast. They place a tooth under a rich kid's pillow, but they meet others who are professionals at stealing teeth and even have a business.
They are taken to the leader, named Loogie, who has been the leader of the business after his two brothers. His business is keeping track of which houses his gang hits, and having them put teeth under children's pillows, and leaving notes for the parents to let them know that their children have lost teeth. Once they have finished the circuit of houses, they go back and collect the money. He gives the four boys a choice, either they work for him and get a 2% cut of the money, or have their penises cut off. They choose to work for him.
The American Dental Association is suspicious about the missing teeth and money, and the leader Dr. Roberts concludes that the culprit is a giant half-chicken/half-squirrel that steals either teeth or money from children as they sleep in order to build some kind of giant nest for its genetically superior and potentially dangerous offspring, and has at least a mild understanding of algebra. Tom Foley, another member believes that the missing teeth and money are due to a black-market tooth racket. The other dentists find this ridiculous. Dr. Foley say's that he has seen it before in Montreal, but nobody believes him, and they again laugh saying that Montreal is a fictional place. Dr. Foley goes to prove his theory is correct while the other dentists turn back to the 'plausible' theory of the chicken-squirrel.
The boys get rather wealthy from the tooth racket, but Cartman decides that they should form their own group and make more profits. When Loogie learns about this, he decides to murder Kenny by drowning him, but he fails because the river Kenny's thrown in is too shallow. A fake news report goes on about a child named Billy Circlovich who needs $600 for a bone-marrow transplant, and has recently lost a tooth, but his parents plan to leave him the money. This turns out to be a trap set by Dr. Foley, to prove the ADA wrong. Although the report was a trap, Billy did have the said illness, and did require the money. Cartman and Loogie fall into the trap, and eventually get caught. Kyle, meanwhile, disappears while questioning his own existence, but soon reappears and alters reality, scaring the police, the ADA, and Loogie's gang away. Loogie decides that the fall of his empire is a good thing, and ends the tooth racket. Meanwhile, Billy is saved as he discovers the "Tooth Fairy's" money under his bed, and happily takes it to his parents. Later, Kenny tries to hop his way out of the river, but then lands in a deep spot and inevitably drowns while Timmy passes by on the bridge.