Question: "The Poor Kid" is the fifteenth season finale of a series created by who ?

Context paragraphs:
South Park (season 15): The fifteenth season of the American animated sitcom "South Park" began airing on Comedy Central on April 27, 2011 and ended on November 16, 2011.  In response to reactions to the mid-season finale episode "You're Getting Old", which seemed to insinuate that creators Trey Parker and Matt Stone were wrapping up the series, Comedy Central proclaimed through the media that "South Park" was renewed for two more seasons, and the duo were signed through 2013.  Shortly before the airing of the season finale episode "The Poor Kid", "South Park" was extended again until 2016, taking the show to 20 seasons.  Parker was the director and writer for all episodes, and Robert Lopez was the writer in this eleventh episode for the fifteenth season.

Mad TV (season 15): The fifteenth season of "Mad TV", an American sketch comedy series, premiered in the United States on The CW on July 26, 2016.  This season features a new cast as well as featuring some original cast members, such as Nicole Sullivan, Alex Borstein, and Will Sasso.  The show aired on July 26, 2016.  The season finale aired on September 27, 2016.

The Price of Free and Fair Elections: "The Price of Free and Fair Elections" is the 18th episode and season finale of the third season of the American political thriller television series "Scandal", and is the 47th overall episode.  It aired on April 17, 2014 on ABC in the United States.  The episode was written by showrunner Shonda Rhimes and executive producer Mark Wilding and directed by executive producer Tom Verica.  The season finale was originally supposed to be the 22nd episode, but because of the show's lead Kerry Washington's pregnancy, the episode count was trimmed by ABC by four episodes, leading the season finale to be the 18th episode.

A House Full of Peters: "A House Full of Peters" is the twentieth episode and season finale of the fifteenth season of the animated sitcom "Family Guy", and the 289th episode overall.  It aired on Fox in the United States on May 21, 2017, and is written by Chris Sheridan and directed by Joseph Lee.

Cause and Effect (Numbers): "Cause and Effect" is the 16th episode and the season finale of the sixth season and series finale of the American television series "Numb3rs".  In the episode, Federal Bureau of Investigation (FBI) agents and mathematicians attempt to find one agent's gun before it is used in a violent crime.  When series creators/executive producers Cheryl Heuton and Nicolas Falacci learned that the number of episodes airing during the season was reduced, they felt that they needed to finish storylines in case the series was cancelled.  To do so, they wrote an open-ended story to serve as either a season finale or a series finale.

Gran Hermano 15 (Spain): Gran Hermano 15 is the fifteenth season of "Gran Hermano", the Spanish version of the reality television series franchise "Big Brother".  The fifteenth season started airing on 18 September 2014 on Telecinco with Mercedes Mila hosting the main "Galas" and Jordi González hosting the "El Debate", a weekly spin-off show airing on Sunday nights.  17 housemates and a goat called Rubia entered the first day at the GH house.  The grand prize this season is €300,000.

2011 V8 Supercar season: The 2011 V8 Supercar season was the fifteenth season of V8 Supercar motor racing and the fifteenth season in which V8 Supercars have contested the premier Australian touring car series.  It was the 52nd year of touring car racing in Australia beginning with the 1960 season, which included the first Australian Touring Car Championship, now known as the International V8 Supercars Championship, and the first Armstrong 500, the fore-runner of the present day Bathurst 1000.

My Finale: "My Finale" is the hour-long season finale for season eight of the American sitcom "Scrubs".  It was originally broadcast as episodes 18 and 19 of season eight on May 6, 2009, and was intended to be the series finale during production.  However, the episode was billed as the "Scrubs finale" as at the time of airing it was unknown whether this would be the series finale or the season finale.  The show ended up returning for a ninth season.  As the show underwent many changes for the ninth and final season, this is the last episode in which all of the main cast appear as series regulars.

The Poor Kid: "The Poor Kid" is the fifteenth season finale of the American animated television series "South Park", and the 223rd episode of the series overall.  It first aired on Comedy Central in the United States on November 16, 2011.  In the episode, Kenny and his brother and sister are sent to a foster home after police discover a meth lab in their house.  As a result, Cartman is left with feelings of loss, since he no longer has someone to ridicule for their poverty.

South Park: South Park is an American adult animated sitcom created by Trey Parker and Matt Stone and developed by Brian Graden for the Comedy Central television network.  The show revolves around four boys—Stan Marsh, Kyle Broflovski, Eric Cartman, and Kenny McCormick—and their bizarre adventures in and around the titular Colorado town.  Much like "The Simpsons", "South Park" uses a very large ensemble cast of recurring characters and became infamous for its profanity and dark, surreal humor that satirizes a wide range of topics towards a mature audience.

Supporting paragraphs: The Poor Kid South Park
Answer: Trey Parker and Matt Stone