The sixth season is the only season of South Park to not feature Kenny McCormick as a main character, due to him being killed off at the end of the previous season in "Kenny Dies." He was revived at the end of the season finale, "Red Sleigh Down", appearing in the last few seconds. This was his sole appearance in the season.
Production
Rise of Butters and Tweek as main characters
Kenny was written off in "Kenny Dies" at the end of season 5 of South Park, though he was mentioned throughout season 6. The other boys mourning Kenny's loss and trying to find a replacement was a reoccurring theme in the season.
For the first five episodes of season 6, Butters fills Kenny's position as the fourth member of "the boys." The rise of Butters as a main character in this season would lay the groundwork for the eventual use and development of Butters' character in future seasons of South Park.
The sixth episode of the season, "Professor Chaos", sees the boys dismissing Butters as Kenny's replacement and Tweek is chosen to fill the position, from episodes 7 to 11.
Kenny's permanent death, subsequent cameos, and resurrection
Initially, South Park was going to continue beyond season 6 with Kenny remaining deceased indefinitely. After several years of needing to devise a number of unique ways of repeatedly killing off the character each episode, Trey Parker and Matt Stone planned to make Kenny's absence permanent. Despite season 6 being well-liked among fans, a small group of viewers protested Kenny's permanent death and even threatened to boycott Comedy Central, the network airing South Park. In response to this backlash, Trey Parker and Matt Stone reversed the decision, acknowledging that South Park wouldn't be the same without Kenny. Consequently, season 6 is the sole season of the series where he was (mostly) absent.
However, Kenny was not entirely written out of the show following "Kenny Dies". He briefly cameoed in the episode "Free Hat" and appeared in flashbacks from "A Ladder to Heaven" to "The Biggest Douche in the Universe", where he appeared as a ghost possessing Cartman's body. Kenny ultimately returned in the final seconds of the finale, "Red Sleigh Down."
Weight loss advocate Jared Fogle incurs the wrath of the town after he announces that he lost weight because he has aides (misinterpreted as AIDS). Meanwhile, the boys use Butters as their spokesman for a Chinese restaurant, as Butters is on punishment and has Cartman covering for him.
The boys and their parents vacation in Aspen. Stan is dragged into a skiing competition with a plot straight out of a rom-com, while their parents are imprisoned at a timeshare seminar.
The boys disguise Butters as a victim of a birth defect so they can win a prize on The Maury Povich Show, but when the freaks go on strike, Cartman disguises himself as an out of control teenage girl in order to get on Maury.
The boys have to sit through Fightin' Round the World, a boring TV show starring Russell Crowe, to see a trailer for the new Terrance and Phillip movie, but risk missing it when Shelley sends the boys out to buy her tampons and the boys try to find another TV to watch the trailer.
Part one of two. The boys try to find a replacement for Butters by holding a contest. Meanwhile, Butters becomes a supervillain after being fired from the group.
Conclusion. Butters discovers that all of his plots for destroying the world have been done before on the animated sitcom The Simpsons. Meanwhile, Cartman creates a miniature society of sea people in his aquarium.
Following the Catholic Church molestation scandals, Father Maxi tries to bring about reform, the South Park parents convert to atheism, and Cartman wins a bet with Kyle that he can defecate from his mouth.
The kids form a club to try to stop Steven Spielberg and George Lucas from editing their classic films, but the townspeople mistake it as a call to free a child murderer named Hat McCullough from prison.
The parents hire Tuong Lu Kim to build a wall around the city to protect the children from kidnappers, but end up letting their kids go after learning that parents are more likely to abduct their own children than total strangers.
The boys build a ladder to heaven to talk to Kenny about a candy coupon. Meanwhile, Cartman accidentally drinks Kenny’s ashes and becomes possessed with his spirit.
Note: This was the first time Trey Parker provided the voice of Kenny McCormick, as he was possessing Cartman's body after he drank his ashes.
The boys go on a quest to return a tape with "evil powers" to the video store before the sixth graders steal it from them. Meanwhile, the parents try to find their kids to explain the context of the porno film they have in their possession.
Mr. Garrison tries to get fired for discrimination by performing inappropriate acts in class with his new teaching assistant Mr. Slave so he can file a lawsuit against the school, but the school administration instead sends the students to a "tolerance camp" to learn how to deal with people of different walks of life.
Chef's parents try to exorcise Kenny's spirit from Cartman. Meanwhile, Stan calls out John Edward for providing false hope to people whose loved ones have died.
In this parody of Black Hawk Down and Three Kings, Cartman tries to bring Christmas to the downtrodden in Iraq to get on Santa's "nice" list. Also, Kenny returns after being "permanently" killed off in season 5, due to fan demand.
