premise: "Merry Christmas, Charlie Manson!" is the sixteenth episode in the second season of the American animated television series "South Park". The 29th episode of the series overall, it originally aired on Comedy Central in the United States on December 9, 1998. The episode was written by series co-creator Trey Parker, along with Nancy M. Pimental, and directed by Eric Stough.
hypothesis: At least three dozen episodes of South Park aired in the United States before "Merry Christmas, Charlie Manson!" originally aired.
reason: Trey Parker wrote the 29th episode of South Park by himself.