Our favorite big boned boy is going to Fat Camp! Cartman's family and friends have intervened and are forcing him to trim down. While Cartman's away, Kenny's star is on the rise when he gets his own reality TV show. He stages a stunt for the finale where he spends six hours in Mrs. Crabtree's uterus.
Allowed to stay home from school one day, supposedly because he was sick, Cartman finds himself having an intervention for his weight issues. His mother and many of the town's people have become concerned about his weight (with the exception of Mr. Garrison, who was only present to see the look on Cartman's face) and so he get sent to a fat camp to lose his weight. When he tries to defend himself with the usual big-boned arguments, his mother reveals that these were all lies, and he is just plain fat.
At school, Ms. Choksondik hands out manatees for the pupils to dissect for biology class, but due to a mix-up, the frogs the 4th graders were supposed to dissect were sent to the aquarium the manatees were supposed to go to. Kyle pays Kenny to eat the dead manatees spleen, but during break, Kenny spews it back up. Kyle, and this time various others, including Stan, Butters and Token, pay him money to eat it back up. Stan and Kyle then realize there might actually be a business in Kenny's willingness to do anything for money.
In fat camp, Cartman tries to break out. After escaping, he sees an ice-cream truck and asks for an ice cream. However, it is a trick - it's a fat camp escapee round-up truck, and Cartman isn't the only one who tried. Another fat kid mentions that they always get them, even though they use the same two trucks (the ice cream truck and a taco truck). Cartman has a brainwave, and says that in jail, he had helped smuggle stuff in by hiding it up his ass. He decides to help the fat kids rebel by smuggling in candy.
Back at town, Cartman apparently arrives, having lost a lot of weight and now being no more fat than Kyle or Stan. However, they do not realize this is actually someone Cartman sent out after breaking him out of drugs rehab to help smuggle candy into fat camp, despite his considerably calmer attitude. When he goes into school, even Chef does not recognize the new "Cartman" at first sight due to the weight loss, despite him wearing the same clothes.
As Kenny does more and more stunts for money, Jesus even goes as far as to call Kenny a prostitute. Since even Kenny does not know what this means, they ask Chef, who cannot explain in terms that they would understand.
"Cartman" goes back to fat camp with various candy treats for the real Cartman to sell. While the fake Cartman is paranoid that he will get caught, the real Cartman begins yelling, and says that he's the one who is putting his ass on the line by being out of the bunk house after hours, smuggling candy in and then selling it on. In light of this, "Cartman" sends the candy over the fence, and Cartman sets up his shop. Since he is making money, he even takes on a friendly attitude to one fat kid who wants to lose the weight because of the ridicule he has to put up with, but doesn't have any self-restraint when it comes to candy. Cartman says that even though people might judge him, candy wouldn't, and as such is his friend. Through this, Cartman is making a lot of money.
Kenny's stunts gain more attention, and eventually he even gets his own show, the Krazy Kenny Show. On this show, he gave his own grandfather a sensual massage, much to the disgust of the live audience. His ultimate stunt was decided to be to climb into a fat bus driver's uterus and stay there for six hours. While promoting the show on radio, Howard Stern runs an experiment with Kenny, Tom Green and Johnny Knoxville to see who is the biggest prostitute, and asks which of the three would take $50,000 in exchange for oral sex. All three say that they would, and a reverse bidding takes place, going from $50,000 to $40,000 to $30,000, until Kenny says he would do it for ten bucks. Knoxville and Green concede, and Kenny subsequently gives Stern a BJ. Unfortunately, this results in him being arrested for prostitution and he is sent to jail.
Kyle and Stan learn of Kenny's arrest and realize the stunt cannot be performed. When "Cartman" delivers the "I've learned something today" speech, though, Kyle finally pulls his hat off and instantly recognizes him as someone other than Cartman. At this point, "Cartman" comes clean. Then, Kyle and Stan have a brainwave and dress "Cartman" up in Kenny's orange parka. Since Kenny had never taken his hood down during the show, nobody would know the difference. "Kenny" climbs into the bus driver's uterus and the six hour countdown begins.
Cartman's illegal candy sales, causes outrage amongst the parents of the other campers, who are furious to see no change in their children and begin to take their kids out of camp. The kids however, feel guilty for betraying their parents and the counselor's trust and come clean. The camp counselors welcome all the kids back, except for Cartman who they banish and send back to South Park for his candy sales.
The countdown ends, but "Kenny" does not come out. The bus driver gives a push, and "Kenny" comes out crushed to death by the pressure in the uterus. The host of the show pays a small tribute to Kenny McCormick, "the boy who would do anything for money", not knowing that the real Kenny has been sent to jail. Then, another boy who nobody recognizes drops out of the bus driver. The host, surprised, asks "Who's that?". The bus driver doesn't seem to know.