The Simpsons jumped the shark in one of my favorite episodes.
Jumping the shark, for those who don't traffic in pop culture shorthand, is the moment in a television show when it begins its decline in quality. The term is named after the notorious episode of Happy Days in which Arthur Fonzarelli literally jumps a shark. The original Happy Days episode lands at the beginning of its fifth season and is followed by a whopping seven more seasons. At this point in the show, Happy Days isn't crappy, it's at its peak.
In this episode, Fonzie is the coolest dude on the show — on television, really — and jumping a shark is actually a parody of coolness. The moment out-cools Fonzie, it crosses this invisible threshold of what we believe the character can do. After jumping the shark, Fonzie is untethered from the reality of Happy Days. The show is thusly knocked off-kilter and begins its decline.
By this logic, the moment The Simpsons jumps the shark should be a creative high point, an episode in which a main character becomes a caricature, that they untether themselves from the reality and logic established until that point.
I believe that episode is "Homer's Enemy" from Season 8. I strongly encourage you to watch the episode. It's a masterpiece, and my synopsis won't do it justice.
The moment The Simpsons jumps the shark should be a creative high point
In short, the Springfield nuclear power plants hires Frank Grimes, an intelligent do-gooder who is immediately put off by co-worker Homer Simpson's gross and dangerous incompetence. Despite always doing the right thing, Frank Grimes' life we learn is a series of disappointments and raw deals.
Enraged by Homer's ability to be rewarded for flippantly strolling through life, Grimes sets out to sabotage his co-worker, tricking him to enter a nuclear power plant design contest meant for children. When Homer wins and is met with support for others at the plant, Grimes becomes unhinged, and impersonating his nemesis' buffoonery, grabs onto high voltage wires, electrocuting himself to death.
And here's the moment, the exact spot, where the show jumps the shark: at Grimes' funeral, a sleeping Homer shouts at his wife to change the channel and everyone laughs, forgetting about Grimes before he's all the way into his grave.
It's one of the funniest moments in the show, it's peak Homer.
Frank Grimes' death is one of the funniest moments in the show
Now by this point, Homer had many unbelievable achievements under his belt. Three seasons earlier, he went to space. But it's not how absurd the moment is that qualifies it for jumping the shark. It's what impact the moment has on the show's character, and through that character, the world.
Before Frank Grimes, Homer is a hapless father with a good heart. After Frank Grimes, he's a caricature of a moron. Before the episode, Springfield treats Homer like another working-class schmuck, surprised by his good fortune. Afterward, he fluctuates between deranged villain, accidental hero and most often walking punchline.
In the following seasons, he begins to do a number of things that only make sense for the post-Grimes Homer. For example, becoming a "prank monkey" in Season 12's "Homer vs. Dignity" — the episode Vox.com's Dylan Matthews marks for The Simpson's jumping the shark.
What makes "Homer's Enemy" great is what causes trouble for The Simpsons down the line: the episode is bitingly meta. Not only are the writer and the audience in on the joke of Homer's superhuman ability to get away with whatever he wants, but, arguably for the first time, so are the citizens of Springfield as they laugh at a man's funeral.
The decline that follow's the episode hasn't been as sharp as the decline that followed the Fonz's shark jump. But the show has never quite recaptured Homer's humanity from the early seasons. Perhaps that's because in "Homer's Enemy" a lack of humanity is the punchline.