Bart and Lisa go to spend the summer at a camp, which proves to be the dangerous Camp Deadly run by Mr. Burns's nephew, Ironfist Burns. His intentions are to make sure that the children suffer and have as little fun as possible.
Bart Simpson's Escape from Camp Deadly is a side-scrolling 2D platform game. It is single-player-only, and the player controls Bart. Lisa's role in the stages is giving Bart boomerangs to use against the various enemies. His default weapon is spit wads, and in the cafeteria stages: the barely edible food offered at the camp.
Source: Wikipedia, "Escape from Camp Deadly", available under the CC-BY-SA License.