Some info and a short description of this South Park episode on South Park Zone:
South Park - Up the Down Steroid is the 113th episode of the Comedy Central series South Park. This South Park episode is a parody of the book Up the Down Staircase. It originally aired on March 24, 2004.
In this South Park episode, Timmy and Jimmy, the two children in South Park having disabilities, are due to participate in the Special Olympics in Denver. In order to cheat in the Special Olympics Jimmy uses steroids and Cartman disguises himself as a child with a developmental disability in order to enter.
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(The complete plot for this South Park Episode)
The Special Olympics from Denver are close and Timmy and Jimmy, the two disabled children in South Park, are due to participate in. Cartman finds out that there is a $1,000 prize for the winner of Special Olympic and he decides to fake being disabled, beats all the handicapped children in the events and wins the prize.To pretend to be handicapped, Cartman undergoes a rigorous sports training-esque montage - set to the music track "Scarface" - that shows a training regime of sitting on the special education bus while taking notes of how "retards" act, cutting his hair badly, studying a Kid Rock performance, modifying his shoes so it looks like he has a club foot, wearing a bicycle helmet, and pulling the string of said helmet so tightly around his face that it both deforms it and affects his ability to speak.
Meanwhile, Jimmy is convinced to take steroids by Nathan to increase his chances of winning. He manages to keep his use of it a secret from everyone except for his training partner and best friend, Timmy. Timmy frowns on this, but, unable to say anything other than his name, Jimmy's name and the quote "Livin' a lie!" he is unable to fully explain the situation to his school counselor, Mr. Mackey. Also, Jimmy starts to neglect his girlfriend and studies and, soon, his steroid use sends him into a steroid rage, causing him to savagely attack his girlfriend and mother (with Samuel Barber's "Adagio for Strings" playing as the atmospheric soundtrack as he loses his mind).
Throughout the episode, Kyle tries to talk Cartman out of his plans. Kyle hates Cartman and has always seen him as a thoroughly ruthless boy, but Kyle sees Cartman's plans as so horrible that he seriously worries that Cartman will go to hell for his antics in this episode. He even goes as far as to call himself Cartman's friend. Cartman dismisses Kyle, claiming that Kyle is the one who is going to hell because he is Jewish.
At the Special Olympics, Jimmy sets multiple records and is declared the winner. Cartman, on the other hand, is so out-of-shape and overweight that he is beaten by all the handicapped children, who have all spent weeks in intensive training before the start of the competition. However, he gets a "spirit award" of a gift voucher to Shakey's Pizza. When he comes up to the stand to collect the prize, Jimmy recognizes Cartman and is about to beat him up for being a cheater, but Timmy intervenes, and Jimmy realizes that he is just as much of a cheater himself too.
Jimmy confesses his drug use to the crowd and returns his medal. As he says that people who are taking steroids are "big fat pussies", and asks for his records to be cancelled, the camera pans across guests Mark McGwire, Barry Bonds and Jason Giambi (athletes who all took steroids). At that point, the people give Jimmy a standing ovation with cheers for being honest, and he says he'll be back next year to "compete with honor."
Cartman then tells his friends that he pretended to be retarded just to teach Jimmy about taking steroids, but they simply stare at him, clearly unconvinced. In response, Cartman angrily says, "Oh yeaah?! Well, you guys are assholes!! Grow up!!" He then walks away.