"Tonsil Trouble" is the first episode of Season Twelve, and the 168th overall episode of South Park. It aired on March 12, 2008.
Cartman gets AIDS due to an infected blood transfusion. Kyle laughs at the irony of the situation, Cartman, looking for revenge, decides to give Kyle AIDS.
Cartman learns that he has to have his tonsils taken out. At first he is reluctant, but agrees when promised ice cream for after the surgery. He wakes up later in a hospital bed, with the procedure complete. Unfortunately, during the surgery, the doctors at Hells Pass Hospital botched the blood transfusion and accidentally gave him a sample that was infected with HIV. Cartman is horrified and asks them if they're joking to which the doctors explain that they aren't. The doctors try making Cartman a little less upset by giving him the ice cream they promised. Cartman, understandably, is only further infuriated by this pathetic attempt at an apology and throws the ice cream on the ground.
At South Park Elementary, the boys are briefed of Cartman's disease and told that they should not treat him differently. Upon discovering this, Kyle finds this to be ironic (because of all the abuse Eric has inflicted upon him and others over the years) and even laughs about it, much to the anger of Cartman.
Cartman has a benefit concert, but only Butters Stotch and Jimmy Valmer show up, as nobody cares about HIV anymore, caring more about cancer now. Elton John was scheduled to play, but instead had gone to a cancer benefit concert, so Jimmy Buffett plays instead, which angered Cartman even more.
The next day, Cartman is talking to the boys about his bennefit concert and Kyle once again bursts out laughing at Cartman's expense. Finally fed up with the laughter, Cartman confronts Kyle about his obvious schadenfreude. Kyle denies that he's finding enjoyment out of Cartman's predicament and claims that he feels sorry for him. Not fooled by the obvious lie, Cartman calls Kyle's bluff and points out that if he felt sorry for him he'd stop smirking. Unable to contain himself any further Kyle retreats to his house, still laughing. Fueled by the desire for revenge, Cartman burglarizes Kyle's house (with the aid of Butters) with a syringe of his HIV infected blood, and injects it into Kyle's mouth.
Upon taking a trip to Hells Pass Hospital, Dr. Doctor informs Kyle and his mother that Kyle has HIV. Kyle freaks out claiming that there's no way he can have HIV, until he realizes that the only plausible explanation was that he got infected deliberately by Cartman. Kyle then runs to school and pushes Cartman over, screaming that he's going to kill him. Stan asks Kyle what Cartman did and Kyle demands Cartman explain why he has HIV. Cartman, isn't very apologetic and denies any responsibility. So Kyle asks Cartman why Butters told him he helped him sneak into his room on Friday, to which Cartman calls Butters a, "taddle-tale". Naturally, unsatisfied and still infuriated Kyle lunges at Cartman and a fight ensues. The fight is broken up by Mr. Mackey. Principal Victoria makes a Cartman apologize for inappropriately giving Kyle HIV and then asks Kyle to apologize for being a "taddle-tale". Leaving the Principal's office, Cartman claims that they are even now, but Kyle doesn't want to hear it and rushes off. Cartman asks Kyle where he's going to which Kyle calmly turns around and tells him that he's going to break everything that he owns and races to Cartman's house Cartman in pursuit. Clearly having a mental breakdown, Kyle destroys as much of Cartman's stuff as he can (such as pulling Clyde Frog's head off). Kyle is then about to break Cartman's Xbox 360 but Cartman convinces him to stop, telling him he knows how he can cure the virus. Intrigued yet still angered, Kyle listens to what Cartman has to say. Cartman says that they should look into the case of former basketball player Magic Johnson, because he "has had AIDS for 50 years and he's still totally fine", according to Cartman. Kyle says that if Cartman is wrong, then he will break his Xbox.
Upon arriving at Magic Johnson's house, Kyle, Cartman and Magic look around to see what might cause his strong resistance to the virus. When going into his bedroom, Kyle and Cartman are surprised to see that the room is full of cash. There are piles of money in obscure places such as the floor, as well as above and under his bed. Magic explains to the boys that he doesn't trust banks, so instead sleeps with all of his money. This sparks the idea that the money might be the cure they're looking for.
The three of them then go to an AIDS research center. They decide to take a risk and have Kyle injected with vast amounts of money into his bloodstream. The experiment is completely successful, and so Cartman and Magic are cured as well.
The news breaks out that the cure for AIDS has been found; Kyle and Cartman are congratulated for it with a Jimmy Buffett concert, singing "Cureburger in Paradise". Kyle tries to tell everyone that Cartman was the one who infected him in the first place, but no one listens to what he says. As the performance goes on, Cartman once again claims they're even and that he's never getting his tonsils out again. Kyle, unsatisfied and understandably still angry, tells Cartman he is still going to break his Xbox despite his statement from earlier, causing Cartman to run after him.