From Wikipedia:

South Park is an American animated sitcom created by Trey Parker and Matt Stone and developed by Brian Graden for Comedy Central. The series revolves around four boys—Stan Marsh, Kyle Broflovski, Eric Cartman, and Kenny McCormick—and their exploits in and around the titular Colorado town.

The town sign of South Park is virtually the hallmark of the series, and has been consistently represented that way for decades since its inception. But despite the praise and honor many label the font itself on the South Park sign as Cibola, when it is in fact Thunderbird, specifically a widened Thunderbird Extra Condensed. This can be seen when comparing the K and R with Cibola’s; unlike Thunderbird, it is slightly different.

Lately South Park movie posters have been using the Behemoth font, specifically PL Behemoth Semi Condensed typeface (see the Streaming Wars poster below).

Additionally, South Park and its franchise has always been accompanied by a certain all caps and cutout font (see second picture below). This font was made only for the series, and to my knowledge was not marketed publicly for commercial use. An emulation with some differences however was used on their official website, it is available for download online as South Park ":)Smilie version", the original production typeface is still unknown.

Poster for the TV special South Park: The Streaming Wars, 2022

South Park Volume 14 DVD cover, 2001

Poster for the movie South Park: Bigger, Longer & Uncut, 1999, featuring perspective lettering loosely based on Beheomoth or a similar heavy Clarendon and the custom South Park font. Credits are set in Futura Condensed with the URL in regular-wide Futura.