Bart brings Santa’s Little Helper to school with him and uses the dog as his subject for Show and Tell. The dog is a big hit with his classmates, but soon becomes a distraction. Bart puts the dog in a coat room where he will not attract attention. But Santa’s Little Helper smells food in the school’s cafeteria and escapes from the room by crawling through an air shaft. Classes become disrupted when children see the dog crawling inside the vent ducts. Principal Skinner orders Willie to retrieve the animal. Willie and Santa’s Little Helper become trapped in a duct and must be rescued by firefighters. Superintendent Chalmers witnesses the debacle and fires Skinner.

Bart feels guilty when he learns that Skinner was dismissed because of the incident with his dog. Skinner invites Bart to his home and the pair become fast friends. Bart is heartbroken, however, when he learns that Skinner has reenlisted in the Army. Meanwhile, Chalmers appoints Ned Flanders as the new school principal. Students immediately take advantage of Flanders’ good nature and take over the building.

Bart admits to Lisa that he misses Skinner as both a friend and enemy—Flanders is too compliant to offer much of a challenge as an adversary. Bart gives Chalmers a tour of Springfield Elementary and shows him that children have completely taken over. Chalmers remains unfazed until he hears Flanders use the word “lord” over the intercom system. Mistaking it for a prayer in a public school, Chalmer’s promptly fires him. Skinner is only too happy to take his position back.