South Park is under attack, again, and Stan, Kyle, Kenny, and Cartman must overcome a series of tower defense challenges to save the town. Players use coins dropped by defeated enemies to construct and upgrade new automated defenses along a linear path. In typical South Park style, towers include homemade fireworks launchers and barbecue grill lasers that bloodily dismember enemies such as cows, Ginger kids, hippies, and Mongolians.
Aside from the towers, each of the four boys can be placed and controlled. They can throw snowballs as a source of extra attack power, collect dropped coins used to purchase towers and upgrades, and trigger a special power unique to each character. These powers range from restoring some of the defended object's health, to clearing the screen of enemies with a fire attack. In single-player, the player switches between each of the four boys, positioning them or taking control as needed. In multiplayer, each player is assigned a character they stick with for that level.
There are 11 levels structured like an episode of the show. Animated stills voiced by the show's actors set up each level; explaining the objective to be defended, and furthering the boys' search for the mastermind behind the attacks. Players can unlock 12 additional playable characters (with unique special abilities) through playing, as well as video clips from the show in a "scrapbook" viewable from the main menu.