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Edna was born January 21, 1961. She holds a Master's from Bryn Mawr College, but is thoroughly jaded, a caricature of the American public school system, as evidenced on the occasion when Lisa steals all the teachers' editions of the textbooks (which contain the answers). Edna genuinely wanted to help people in need but it after years of frustration thanks to the school, and Bart Simpson in particular, this wore away on a somewhat tragic note.
There is some inconsistency about Edna's origins. Though she is said to have come to Springfield to begin teaching, she can be seen running through the background in Springfield High School in when Clancy Wiggum is being videotaped as a hall monitor. Krabappel, like many other teachers at Springfield Elementary School smokes heavily, especially during school hours. It was also once implied that Edna Krabappel drinks heavily, as when Marge arrived at the school to use a restroom and stumbled upon the horrible conditions of the school, she noticed Edna Krabappel's class where Bart felt he had to sleep in class and uttered "stupid teacher," to which Edna was also sleeping in a similar fashion to Bart and uttering "stupid hangover" and once got fired when she became drunk (although the latter instance wasn't her fault, as her drink was spiked by her students in order to help her become laid back.).
The most recurring theme about Edna is her non-existent love life, and as a result, loneliness and wish for male company. She is divorced; her husband ran off with their marriage counselor. She has talked about her ex living somewhere else exotic, but at one time, a man at the local gas station, while diagnosing a fault with her car, tastes sugar in the gasoline and states "Your ex-husband strikes again! " As a result, she severely misses male company, and it is occasionally implied that she feels her biological clock ticking. She is shown as very sexually aggressive: she tried to pick up both Joey Kramer (Aerosmith's drummer) and Homer Simpson and like him. She had a relationship with Principal Seymour Skinner. She can be seen at a Green Day concert on top of Seymour's shoulders wearing a T-Shirt saying "Not my boyfriend" with an arrow pointing down at Skinner.
It's shown in a flashback that Edna was in a serious relationship with Moe Szyslak when she first moved to Springfield, before meeting Skinner or even becoming a teacher. She was about to run away with him (and possibly get married) but then changed her mind when she met Bart Simpson, a student she believed needed help (it was revealed, however, that Bart was just stalling while Nelson Muntz stole microscopes from the school). At the end of the episode, Moe and Edna are a couple once again, much to Skinner's jealousy when he caught them making out on school property. Indeed, Edna appears to be the object of many a man's desire, as evident by Sideshow Bob's outrage when his romantic date with her is ruined by a spying Bart: "You only get one chance with Edna Krabappel!" One time, during an "edu-tainment" show at Springfield Elementary School, she did a balloon dance wearing nothing but balloons while she pops them to the tune of "Fever," mortifying the audience (especially Bart, who even went as far as to say "kill me" from witnessing it). She often has dinner at The Pimento Grove with her on again - off again dates. She is now married to Ned Flanders.
The Simpsons: Tapped Out
Behind the Laughter
Her last name is a play on the fruit "crabapple" and it is also a reference to the teacher Miss Crabtree from the 1930s Little Rascals serials. Part of the original joke of her last name was that nobody ever mispronounced her name and called her "Miss Crabapple", Milhouse was the first to make this joke which had the other students in class amazed and feeling stupid for not noticing it before.
On October 25, 2013, Marcia Wallace died in her home in Los Angeles after a battle with pneumonia. Due to this, Simpsons executive producer and showrunner Al Jean revealed that Edna was not going to be the character that was being killed off in the season 26 premiere but the character will now be retired. It is currently unknown how the character will be retired.