What is the title of South Park's three-part season 11 story about a fantasy realm?

South Park’s three-part season 11 story about a fantasy realm is Imaginationland. The arc begins when Cartman claims he has seen a leprechaun, leading Stan and Kyle to a strange dimension populated by characters from humanity’s imagination.

The story expands into a conflict between the realm’s beloved imaginary figures and invading forces. It mixes South Park’s original characters with recognizable fantasy, literary, and pop-culture archetypes, turning the imagined world into both an adventure setting and a parody of modern entertainment.

The trilogy consists of “Imaginationland Episode I,” “Imaginationland Episode II,” and “Imaginationland Episode III.” The first episode aired on October 17, 2007, and the complete arc later received an extended home-video release titled Imaginationland: The Movie, which included previously unreleased footage.

The production was unusually ambitious for South Park. Parker and Stone initially considered developing the idea as a feature film, but adapted it into a television trilogy. The arc won the 2008 Primetime Emmy Award for Outstanding Animated Program for programming one hour or more. “Black Friday” is another South Park multi-episode story, but it belongs to season 17 and focuses on a different theme.