Shelly Marsh is a recurring character from the animated series South Park, known as Stan Marsh's older sister, Randy and Sharon’s daughter, and a generally aggressive bully who often torments Stan, calling him a "turd," though she's shown more depth and character development in later seasons, sometimes revealing a kinder side or dealing with relatable teenage issues like braces and relationships, with her character being partly based on co-creator Trey Parker's own sister. 