Homer becomes the Springfield Elementary School's "safety salamander" to make an amend to stop Lisa's frustrations against men. After he saves many drivers from a multiple car crash, Homer runs for mayor.
The family goes to the Springfield Mall to buy a Father's Day gift for Homer. He is impressed by Bart's gift – a Leather Buddy multi-function knife – but Lisa's gift, a book she created, with caricatures of herself and Homer as unicorns, doesn't go over so well. In a half-hearted attempt to make Lisa feel better, Homer hangs the book on the refrigerator, but it quickly becomes a water-soaked glob of paper. He then blames the magnet he hung it on which was actually a gift from Lisa for his birthday, then she runs off crying.
Lisa takes out her frustrations at school, and her parents are called to talk with Principal Skinner. School psychiatrist Dr. Loren Pyror determines Lisa has a development disorder, which can only be resolved by Homer trying to make amends. He does so by dressing as the "Safety Salamander" and giving safety talks at school, as for Skinner's suggestion. However, a fireworks display during a school assembly causes a fire.
Meanwhile, Bart, on a dare from the bullies, steals a "Bart Blvd." street sign. This leads to a fiery multi-car pileup when Cletus is unable to find Bart Boulevard (looking for the hospital where his son was born). Police cars, fire trucks and ambulances race to the scene but crash into the wreck, making matters worse.
Homer, still dressed in his Safety Salamander costume, runs to the rescue, extricating people who were trapped in their cars just before the pileup explodes in a fireball, including Smithers, Dewey Largo, Drederick Tatum and Nelson. Homer gets a rousing reception, and Mayor Quimby is blamed for the bumbling response. Springfield residents pick apart Quimby's administration for other failures, and demand a recall election.
The election causes 200 of Springfield's residents to run. On Lisa's suggestion, Homer plans to run for mayor, playing on his popularity as the Safety Salamander. Marge wants to wash the costume, since it is too dirty and Homer puked inside it. Marge does so, but during a debate forum, the costume falls apart, disappointing the crowd. People don't like Homer as a normal person, and eventually none of the new candidates gains at least 5% of the votes to oust Mayor Quimby. However, Lisa confides in Homer that she is very proud of him and glad he is her father. They start dancing at the end of the debate, but Homer still feels his tail, much to his disgust.