In discovering the joy of playing Dash Dingo, Lisa neglects to study for her upcoming test, which she later relents to cheating upon in order to pass. When the resulting grade raises the school's state average and qualifies it for financial aid, the intendance forces her to cover up all wrongdoing. Meanwhile, Homer raises a baby lobster to beat the high store prices of adults.
After yet another long Sunday morning at church, Homer takes the family to a local store for Sunday brunch, by eating the free samples. After being stuffed into a freezer, by Homer who wants some ice cream, Lisa comes down with a bad cold and is forced to stay home from school. In order to keep her mind off school, Marge encourages Lisa to play one of Bart's video games. Lisa becomes addicted to playing the game "(Dash Dingo)". She claims to still be sick for many more days to play video games, until Marge stops believing her.
When Lisa returns to school Miss Hoover has her take a test on The Wind in the Willows, a book she was supposed to have read while she was sick. Lisa panics and excuses herself to go get a drink. While in the hallway she runs into Bart who refers her to the boy's restroom. There they meet Nelson who is selling test answers. Lisa completes the tests with Nelson's answers and gets an A+++. Later she is summoned to Skinner's office. He tells her that her A+++ increased to the school's GPA allowing the school to receive an assistance grant. Lisa admits to Skinner that she cheated. Both he and Chalmers agree that Lisa's cheating should be kept quiet so that they can still get the grant money, Lisa initially refuses to hold her tongue until she is taken on a tour of the school to show how under funded and in desperate need of money the school is for even the most basic of equipment and she relents. At the ceremony, however, Lisa's inability to hold the truth for her own guilt even at the expense of others shines through and confesses to cheating on stage. The comptroller decides to give the school the money anyway to reward Lisa's honesty. All the family, except for Bart, leave the auditorium. It is then revealed that the ceremony was fake, orchestrated by Principal Skinner and Chalmers who knew Lisa well enough to know what would happen and the comptroller was really Otto wearing a latex mask. The real ceremony takes place without Lisa's knowledge and the real comptroller gives the school the grant money.
Meanwhile, Homer buys a small live lobster at the grocery store and fattens him up with plans to feed him to the entire family. When it's time to eat him, Homer has a change of heart and keeps the lobster as a pet naming him Mr. Pinchy. Homer unwittingly gives Mr. Pinchy a hot bath only to have boiled him to death. Homer mourns and cries over Mr. Pinchy's death by eating the whole lobster by himself, as he feels "Pinchy would've wanted it that way."