There's no new Simpsons tonight, so, in honor of the late, great Marcia Wallace, might I recommend breaking out your DVD collection and watching one of these classic Edna Krabappel episodes:
Bart the Lover, Season 3
If there's a better Mrs. K episode, I can't think of one. This shows Edna at her most complex and human -- and Bart too, for that matter. Wallace won an Emmy for this one.
Bart Gets an F, Season 2
And speaking of emotions we don't often see from Bart, the climax of this one -- where he breaks down in tears on finding that he failed his test despite really trying his hardest this time -- shows us a seldom-seen side of both characters, without giving in too much to sentimentality. I love Mrs. K's attempt to comfort Bart -- "I would have thought you'd be used to it by now!" could so easily have come across as sarcastic, but Wallace chooses to read it as a gentle, tender statement. Now that's comedy.
The PTA Disbands, Season 6
So many classic moments in this episode purple monkey dishwasher. It's Simpsons at its satirical finest, highlighting the conflict between teachers and administration, the public's simultaneous desire for better schools and lower taxes, and the terrifying reality that if you pick up some random person off the street, they'll be a worse teacher than Miss Hoover or Mrs. Krabappel. And the resolution is so ludicrous that it can only serve to hang a lampshade on how intractable these issues really are.
Grade School Confidential, Season 8
Mrs. Krabappel and Principal Skinner were in the closet making babies and I saw one of the babies and the baby looked at me.
The Ned-Liest Catch, Season 22
Say what you will about modern-era Simpsons, pairing off Ned with Edna was a rare and legitimately pleasant surprise. It's not the sort of thing I would ever have seen coming, but it makes its own unexpected kind of sense -- two characters who have seemingly nothing in common but their loneliness, but who complement each other so thoroughly and who can each stand to learn so much from the other. This episode highlights how difficult those differences can be, and they almost don't make it as a couple -- but, thanks to an Internet vote, they stay together.