Heidi Turner is a popular, kind-hearted fourth-grade girl from the animated series South Park, known for her role as Cartman's girlfriend in seasons 20 and 21, during which she transformed into a cynical, manipulative version of herself due to his influence before breaking away to reclaim her true self. Initially a background character, she became central to major story arcs involving social media, environmentalism (Troll Trace), and the toxic dynamics of her relationship with Cartman.