Sweet Seymour Skinner's Baadasssss Song (S05, E19-100)

"I finally have time to do what I've always wanted: write the great American novel.
Mine is about a futuristic amusement park where dinosaurs are brought to life
through advanced cloning techniques.  I call it 'Billy and the Cloneasaurus'."

Plot Summary
Desperate to find something for show and tell, Bart decides to bring along Santa's Little Helper.  While the dog is a hit at the presentation, Martin pressures Bart to put the dog in the closet so he can show off his geode.  While in the closet, the dog is able to make his way into the air vent, causing chaos.  Skinner orders Groundskeeper Willie to grease up and go into the vents to capture the dog.  Willie does so, but winds up in the vent above the gymnasium, too high up to leave.  The fire department is brought in to help them out, while Superintendent Chalmers catches wind of the incident and fires Skinner.

While Bart mistakes a spider bite for guilt, Chalmers hires the head of the PTA, Ned Flanders, as the new principal.  Ned, who remembers his parents being rule-less beatniks, is unwilling to enforce discipline.  He installs an "honor system", and soon the school quickly descends to chaos as teachers refuse to leave the lounge.  Meanwhile, Bart sees Skinner in the Kwik-E-Mart in civilian clothes, and then later in the laundromat looking rather pathetic in both instances.  Bart feels sorry for him and goes to visit Skinner at his house.  The two spend more time with one another, but Skinner deeply misses the school still.  Only one other thing has given Skinner's life meaning, and its what Skinner decides to go back to: the army.

Missing Skinner as a friend, and even more so an enemy, Bart decides to get Skinner back into the school.  He finds Skinner and convinces him to come back, after Skinner realizes that the army hasn't really changed at all.  Bart's big plan is to have Chalmers fire Ned after seeing the state of the school.  However, Chalmers actually doesn't care, noting that all public schools are going to devolve to this level sooner than later.  At that moment, Ned gives a message on the PA that includes the phrase "thank the Lord".  Realizing that its a prayer in a public school, Chalmers becomes outraged and fires Flanders, hiring Skinner back if only because "he knows the students' names".  Skinner thanks Bart for what he's done, and the two happily become enemies again.

Quick Review
Most shows celebrate 100 episodes in some big way.  The Simpsons celebrate 100 episodes with a passing mention of milestones in the chalkboard gag and then presenting a silly story featuring Bart's principal.  The 100th episode of the series is by no means the best of the 100, but its still a funny episode that delivers plenty of humor and a plot that sets up those jokes well.  Skinner is a difficult character to mess up, but this episode does a fine job with his character and the relationship between him and Bart.

Final Score: 8.8