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, decides 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's a photo of Woodrow.
Meanwhile, Marge notices that their dog 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's looking for since none of the usual suspects taught Todd to curse.
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 theatre, laughing after watching "Ernest Needs a Kidney," and then is upset and 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 children overhears 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 profanity. Homer criticizes him about his moustache 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 he got out of the Navy, his constant cursing almost costs Clancy his job as a baby photographer but her mother was able to curtail that by using a swear jar. 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 profanity.
At school, Bart tries to cheer her up saying she can date the men in the school. However, Edna point out their flaws like how Skinner still lives with his mother, and the gym teacher drinks a lot. Remorseful, Bart tells the family what he has done, and Marge tells him, "You did a very cruel thing." Homer said Bart should tell the truth to Edna, but Marge said that he can't because the truth would humiliate her. Lisa suggests they write a letter to tell Edna goodbye without hurting her feelings, and after several attempts they produce a romantically diplomatic letter where Woodrow says he must go, but will always remember Edna. Homer repeatedly pitches the same idea: "I am gay.", but Marge keeps turning it down stating it's too disrespectful. However, he helps the family create an acceptable letter. The letter is a success: Edna is left feeling sorry that Woodrow is gone, but happy with how things ended. She suggests to Bart that they spend his last day of detention outside and he agrees.