"Bart the Lover" is the fifteenth episode of Season 3.
Mrs. Krabappel's new pen pal has the name of the 28th president, the face of Gordie Howe, and the lines of a food-obsessed Frenchman. Is he the perfect lover, or Bart's latest practical joke? Meanwhile, Homer starts building a doghouse, and learns to give up swearing.
A yo-yo craze sweeps through Springfield Elementary School, much to Edna Krabappel's annoyance. At the same time, she is feeling increasingly lonely and places a personal ad in the newspaper, ending with "Object: SAVE ME." Bart, who has been given one month of detention for breaking the classroom fish tank with a yo-yo, discovers the ad and, realizing it is Mrs. Krabappel's, chooses to pull a prank and respond by mail with a new alter-ego. Bart pretends to be an adult male called "Woodrow," named after former President Woodrow Wilson. For romantic writing to send to Edna, Bart borrows a couple of lines from Homer's old love letters to Marge, then watches old movies as inspiration for more writing. A chain of romantic correspondence follows, where Edna sends Woodrow a sexy photo of herself and Bart reciprocates by sending her a picture of ice hockey player Gordie Howe, claiming that it is a photo of Woodrow.
Meanwhile, Marge notices that Santa's Little Helper needs a new dog house. She wants to buy one, but Homer says that he can save money by building one instead. His infuriating attempts at constructing the dog house cause him to curse loud enough for Todd to overhear. At night, Ned is upset when he hears Todd say "hell no" and "damn" at the dinner table. He seeks out ways to find the source of the cursing. Ned presumably comes to a dead end when he can't find what he is looking for since none of the usual suspects taught Todd to curse (i.e: bumper stickers, T.V., grandparents, comic books, and Rod).
Edna takes the next step, asking if she and Woodrow can meet in person, have dinner, and return to her apartment for some "home cookin.'" Bart, as Woodrow, writes a letter making a date to meet at The Gilded Truffle for dinner, and Edna is excited at the prospect of meeting Woodrow. Bart, however, has no intention of keeping the date, and while Edna waits in vain for Woodrow at The Gilded Truffle, Bart goes to the movies. Later, he comes out of the movie theater, laughing after watching "Ernest Needs a Kidney," and then feels guilty when he sees Edna crying while sitting at a table by herself.
The next day while Ned tries to come up with more sources, he and his sons overhear Homer curse in his failed attempt to build a doghouse for Santa's Little Helper. Ned discovers he was the source and confronts him for cursing out loud that lead to Todd picking up foul language. Homer criticizes him about his mustache in retaliation, which Ned promises to shave off in return for Homer's cutting back on the swearing. At night when Homer claims that it's too late for him to stop swearing, Marge disagrees and reveals her own experience with her father, Clancy, while she was growing up:
When Clancy got out of the Navy, he developed a swearing problem that was so bad it almost cost him job as a baby photographer. So to curtail it, Marge's mother, Jackie, made a "Swear Jar" and had Clancy put money in it every time he said a curse word.
Homer promises to put money in a "swear jar" -- 25 cents for each curse. However before going to bed, he asks Marge some questions just to understand the ground rules. Homer's constant cursing rapidly fills the jar, although he does gradually curse less and less. Eventually, Homer becomes frustrated while building a doghouse. Combined with seeing a clean-shaven Ned thank Homer because his beardless look enabled him to star in a TV commercial, Homer loses his cool, and kicks the doghouse to pieces—but manages to avoid swearing. Marge and Lisa then surprise Homer with a brand new doghouse, easily bought and paid for with the money from the swear jar. They have an added bonus, Duff Beer as a gift for Homer for his commitment in curtailing the use of swear words.
At school, Bart tries to cheer his teacher up by pointing out that there's plenty of other guys out there, such as the men who work at the school. Edna rejects the prospect of dating any of the school's male employees and points out there biggest flaws (like how Skinner still lives with his mother and how the gym teacher drinks a lot). Remorseful for what he's done to his teacher, Bart admits what he did to his family, which they all call him out on. Homer argues that Bart should just admit the truth to his teacher and face the consequences--but Marge claims that wouldn't be a good idea, as the truth would humiliate Edna. Lisa suggests that writing a letter that tells Mrs. Krabappel that even though Woodrow's leaving and will never see her again, he'll always love her and keep her in his heart. After several attempts, during which Homer repeatedly pitches the same idea ("I am gay," but Marge keeps turning it down because it's too disrespectful), the family produces a romantically diplomatic letter that proves to be a success. After delivering the letter and Edna reads it, she's sad that Woodrow's gone but is also happy with how matters ended. She suggests to Bart that they spend his last day of detention outside and he agrees to that.