Some info and a short description of this South Park episode on South Park Zone:
South Park - Kenny Dies is episode 78 of the Comedy Central series South Park. It was originally broadcast on December 5, 2001. Kenny dies? We heard this before many times. Notably, the gag of Kenny dying in almost every episode was dropped after this episode, and he did not reappear until South Park episode "Free Hat".This was the final appearance of the "4th Grade" title sequence which was first seen in "4th Grade".
Kenny contracts a muscular disease and dies kind of "permanently".
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(The complete plot for this South Park Episode)
The episode begins in an abortion clinic with a woman giving her permission for doctors to use her aborted fetus for stem cell research. However, the truck transporting the fetuses to a medical research facility is destroyed in an accident. Its cargo is noticed and subsequently stolen by Cartman, riding his bike and singing Sheena Easton's "Morning Train". Cartman intends to resell the fetuses for a tremendous profit. This goal leads him to call various institutions in the style of a fast-talking agent, with the famous recurring line "you're breaking my b**ls, here", finally landing a deal with a government organization. To his dismay, the government puts a ban on stem cell research immediately afterward.Meanwhile, Kenny is diagnosed with what is presumably muscular dystrophy, and his friends and family are told that he will probably die. The boys are shocked and saddened by the news, but do everything they can to support him and keep him company during his stay in the hospital - all but Stan, who cannot bear to see Kenny dying and refuses to visit him. This marks one of the few episodes in which Kenny's friends mourn his death. Cartman, in the meantime, has a doctor explain to him how stem cells actually work, and learns that they might be used to help Kenny. Cartman also mentions using stem cells to duplicate a Shakey's Pizza restaurant, although the researcher advises him that lumber would be better suited for that task. Cartman gives a speech to the House of Representatives on behalf of stem cell research. He ultimately succeeds in getting the ban lifted by singing "Heat of the Moment" by Asia, and begins visiting laboratories around the area to collect more fetuses.
Stan, with the supporting words of Chef, finally gets up the courage to come visit Kenny in the hospital. Unfortunately, Kenny has finally died from the disease. On hearing that Kenny's last words were "Where's Stan?" he accuses himself of being Kenny's worst friend. During the funeral, Cartman bursts in and exclaims that a miracle has occurred. He drags Stan and Kyle away to show them how he has manipulated the stem cells from his fetuses into building his very own Shakey's Pizza. Kyle promptly beats up Cartman, realising that Cartman had pretended to take Kenny's illness seriously in order to get the ban on stem cells lifted just so he could make a profit off them, therefore allowing him to make his own Shakey's Pizza. Stan is relieved when he realizes Cartman was Kenny's worst friend.