Like you, we don't really see how South Park could be made into a playable RPG, but it seems that the development team at Obsidian knows.
"South Park: The Game is an epic role-playing adventure that will allow the user to befriend Stan, Kyle, Cartman and Kenny and explore the quiet little mountain town like never before," Obsidian revealed in a press release.
"Our goal is simple: to put creative talent first," said Danny Bilson, EVP Core Games, THQ. "Matt and Trey are arguably two of the most important comedic talents of their generation. Bringing their vision of South Park to the interactive space is a dream-come-true."
Obsidian Entertainment are best known for Fallout: New Vegas and Alpha Protocol.