"The Death of Eric Cartman" is the sixth episode of Season Nine, and the 131st overall episode of South Park. It aired on April 13, 2005.
Stan, Kyle and Kenny (along with the rest of the 4th Grade) have had enough of Cartman and ignore him, which leads him to think he has died and has become a ghost. Cartman tries to get into heaven by doing "good deeds", but fails in the end.
At Stan's house, the boys wait for Sharon to return home with KFC. She arrives and asks the boys to help her take the shopping bags in. As they do so, Cartman eats all the skin off the chicken and the boys become incredibly angry at Cartman for eating the best part of the KFC (which causes Kenny to burst into tears). Realizing that he thrives on the fact that they rip on him, they decide that the best way to deal with him is to completely ignore him. Cartman, however, discovering that nobody seems to see or hear him, believes that he has died and become a ghost. He believes this to be confirmed when he goes home and sees a casket-like box coming out of his house, which the men carrying it mentioning that it was filled with chicken skins, when in reality, it is the toilet that Cartman destroyed with his last use of it. He also hears his mother screaming as she has sex with a plumber, mistaking it for crying over his death.
While most of the kids in South Park soon join in Stan, Kyle and Kenny's resolution to ignore Cartman, Butters is unaware of the movement, and so greets Cartman as he passes by. They then both believe that Butters is somehow psychically able to see him, and set off to try to allow Cartman to go to Heaven (Cartman claims he can't go to hell because he is not black). First, Cartman has Butters apologize to everyone on his behalf; when that fails to allow Cartman to pass over, Butters makes a list of all of Cartman's sins, and they try making amends to various people Cartman has wronged via gift baskets. When this too fails, Cartman goes berserk, destroys Butters' room with a baseball bat, and ends up getting Butters thrown in an insane asylum and grounded, where Butters is anally probed by a machine for over 14 hours.
After breaking Butters out, the two consult a psychic named Doctor Lindsay, who suggests that God has kept Cartman on Earth to help with some kind of crisis. When they hear of a hostage situation at a Red Cross the two set off and Cartman manages to stop the criminals by moving things around. The robbers are merely befuddled at the child's behavior, which provides enough of a distraction for the police to end the hostage situation. Cartman is credited with saving the day, "armed only with the weapon of confusion," as a news reporter put it. After this, Cartman's classmates arrive and tell him they're willing to be his friend again, thinking he has truly changed. When they leave, Cartman — mortified and furious that he had apologized to everybody and been fooled — again goes berserk and inexplicably blames Butters. After Cartman angrily vows revenge on Butters, he is caught by his parents and a doctor from the asylum (still carrying the anal device), who suggests Butters needs more therapy.