Since this seems to be the trend, here's my entry:
To approach this episode is like approaching the foundation of a famous fixture, like the white house. Sacred and untouchable. It represents when alot changed with the show, things began in the first season started coming to fruition, characters developing and taking shape. They got just the right balance of humor and drama.
This episode has been airing for nearly 20 years now and as such, has been reviewed countless times by people from all walks of life and with every opinion under the sun. At the risk of repeating what has come before I will focus on a few stand out things this episode showed me over the years after repeated viewings.
First, just because a show is animated, you can still take it seriously. This is the most important to me, even though it sounds so simple. Up until this episode, and realistically the Simpsons in general, you would have been laughed at if you tried to inject emotion into any kind of animated television show. I don't count cinema because Disney worked with animals and as such, it was all too easy to garner sympathy and the feature length meant people were stuck there for the duration, unlike a 30 minute television sitcom. This was best achieved by this episode, in my opinion, the weight given to it by Yeardley's performance as Lisa did so much to make the episode. Dan Castelleneta gave a standup performance too, with the scenes in the museum and later towards the end during the whole 'baboon' debacle. I think it really surprised people the first time this aired, when that scene in the train station was made as emotionally devestating and then immediately uplifting with that simple note Bergstrom gave to Lisa. You are Lisa Simpson. That note has had an impact on her characterization lasting up to this day. All of this and I haven't even mentioned Dustin Hoffman, whose portrayal of the substitute is what made the episode possible in the first place. It's a minor thing nowadays to have a bigname guest star on the Simpsons, they've had so many. But this was season two, so early he didn't even want his name tainting peoples opinions of the episode (possibly of himself as well) merely by his presence. By the end of the story it never once crosses your mind (well except for that one reference with Mrs. Krabapple) that this is a huge Hollywood actor and you have completely bought into his being the best substitute in the world. That's a guest STAR. That's how it's done. No silly cameo, no cheesy story or awkward insertion into the plot. It just works.
Now for the other side of things, this show also demonstrates the strength of the two story structure with Barts completely unrelated bid for class president. This is where all the laughs, the lighter moments to balance the drama of the other story came from and it was hilarious. This episode developed so many early characters like Ralph and Martin into what they eventually became later in the series. And the political satire was spot on, showing that at it's most simplistic form, politics is a popularity contest but if you only win votes based on empty promises and words it's still possible to lose because you've surrounded yourself with people who are equally uncaring about the state of things. That's heavy stuff for an animated show to cover, and is often overlooked due to the strength of the other half of the story but I think is rely one of the more brilliant moments on the show.
So having covered the two seperate stories we now arrive at end of the episode with a scene that still gets me to this day. Here, Homer makes things right between himself and Lisa after botching his attempt at being a caring parent so thoroughly you have to wonder how he ever got Marge in the first place. After that, he manages to, with a few simple words, take all the sting of defeat away from Bart (let the baby have his bottle) and compared to how they usually show his and Barts relationship these days is one of the sweeter moments they share in the series. It wraps both plotlines up very neatly and let's you know things have safely been set right. Once Homer fixes things with both kids, and replaces Maggies pacifier, since all things being equal he's gotta make it perfect, the episode ends with the family at the happiest point they are during the whole episode, and if that isn't closure I dont know what is.
I'll just add the rating I gave it in the poll: 5/5