Question: Which American animated television series created by Trey Parker and Matt Stone features a character called Butters who thinks up schemes to take over the world in its 86th episode?

Context paragraphs:
Eric Cartman: Eric Theodore Cartman, often referred to as just Cartman, is a main character in the animated television series "South Park", created by Matt Stone and Trey Parker, and voiced by Trey Parker.  Cartman, generally referred to by his surname, is one of four central characters in "South Park", along with his friends Stan Marsh, Kyle Broflovski, and Kenny McCormick.  Cartman first appeared, originally named Kenny, in prototypical form in a 1992 animated short "Jesus vs. Frosty", and a 1995 animated short "Jesus vs. Santa", and first appeared on television in the pilot episode of "South Park", "Cartman Gets an Anal Probe", on August 13, 1997.

Chef Aid: "Chef Aid" is the fourteenth episode in the second season of the American animated television series "South Park".  The 27th episode of the series overall, it originally aired on Comedy Central in the United States on October 7, 1998.  The episode was written by series co-creators Trey Parker and Matt Stone, and directed by Parker.  Guest stars in this episode include Joe Strummer, Rancid, Ozzy Osbourne, Ween, Primus, Elton John, Meat Loaf, Rick James, and DMX.

South Park (season 10): The tenth season of "South Park", an American animated television series created by Trey Parker and Matt Stone, began airing on March 22, 2006.  The tenth season concluded after 14 episodes on November 15, 2006.  This is the first season in which Kenny does not die and the last season featuring Isaac Hayes (the voice of Chef) as Hayes quit the show following the backlash behind season nine's "Trapped in the Closet" episode.  This season also had a minor controversy when the Halloween episode "Hell on Earth 2006" depicted "The Crocodile Hunter's" Steve Irwin with a stingray lodged in his chest getting thrown out of Satan's Halloween party for not being in costume.  Episode 2 in this season is the last one with the Braniff Airlines logo.  All the episodes in this season were written and directed by Trey Parker.

South Park (season 2): Season two of "South Park", an American animated television series created by Trey Parker and Matt Stone, began airing on April 1, 1998.  The second season concluded after 18 episodes on January 20, 1999; it remains the longest season of "South Park" to date.  While most of the episodes were directed by series creator Trey Parker, Season 2 includes two episodes directed by Eric Stough.

South Park (season 9): Season nine of "South Park", an American animated television series created by Trey Parker and Matt Stone, began airing on March 9, 2005.  The ninth season concluded after 14 episodes on December 7, 2005.  All of the episodes in the ninth season were written and directed by Trey Parker.

Major Boobage: "Major Boobage" is the third episode in season 12 of the American animated television series "South Park".  The 170th episode of the series overall, it originally aired on Comedy Central in the United States on March 26, 2008.  The episode was co-written by series creators Trey Parker and Matt Stone; it was the first South Park episode since 2000 not solely written by Parker, ending a streak of 120 consecutive straight solo episodes.  The previous episode co-written by Stone was "The Tooth Fairy's Tats 2000".

South Park (season 7): Season seven of "South Park", an American animated television series created by Trey Parker and Matt Stone, began airing on March 19, 2003.  The seventh season concluded after 15 episodes on December 17, 2003, and was written and directed by Trey Parker.

Simpsons Already Did It: "Simpsons Already Did It" is the seventh episode of the sixth season of the American animated television series "South Park", and the 86th episode of the series overall.  It originally aired on Comedy Central in the United States on June 26, 2002.  In the episode, which continues on from the events of the previous episode "Professor Chaos", Butters thinks up a series of schemes to take over the world, but realizes that each one has already been performed on "The Simpsons".  Meanwhile, Ms. Choksondik dies and Cartman, Kyle and Stan think that they are responsible.

South Park (season 8): Season eight of "South Park", an American animated television series created by Trey Parker and Matt Stone, began airing on March 17, 2004.  The eighth season concluded after 14 episodes on December 15, 2004, and was written and directed by Trey Parker.  The season deals with various topics that were relevant at the time of release.  The episodes portray a spectrum of topics, from effect of large scale retails corporations to immigration.

South Park (season 6): Season six of "South Park", an American animated television series created by Trey Parker and Matt Stone, began airing on March 6, 2002.  The sixth season concluded after 17 episodes on December 11, 2002.  This season is notable for being the only one without Kenny as a main character, as he was written off in the previous season.  Kenny, however, plays a part in some episodes without appearing and returns at the conclusion of the final episode.

Supporting paragraphs: Simpsons Already Did It South Park (season 6)
Answer: South Park