"I Married Marge" is the twelfth episode of the Season 3.
In a flashback, the year is 1980, and Homer and Marge are dating. After seeing a Star Wars movie, they get busy afterwards - and Marge finds out she is pregnant with Bart. When Homer finds out, he proposes to her, and then tries to find a higher paying job. He goes to the new power plant, only to be rejected. When the baby's possessions are repossessed, Homer chooses they will be better off without him - until Marge comes to find her husband.
Marge and Homer are worrying that Marge may be pregnant again. After a home pregnancy test gives inconclusive results, Marge drives to Dr. Hibbert's office. Homer begins to tell Bart, Lisa, and Maggie about how he and Marge got married, and Bart's birth thereafter.
Homer begins his story in 1980, while he was working at a miniature golf course and still dating Marge. One night on a romantic date, after seeing The Empire Strikes Back, Homer and Marge make love inside of a golf course castle. Shortly after, Marge discovers that she is pregnant. Homer decides to propose to Marge, and she eagerly accepts. The two marry in a small wedding chapel across state lines, while Marge is pregnant. The two spend their "wedding night" at Marge's parents' house, sleeping on a couch in the living room. Needless to say, this aggravates Marge's mother and sisters extremely, who all despise Homer.
Unfortunately for Homer and Marge, Homer's wages are not enough to pay for his new family. Homer attempts to apply for a job at the Springfield Nuclear Power Plant, but his interview goes horribly, partly due to his own ineptitude and the blatant favoritism displayed by Waylon Smithers (the other two applicants are members of his college fraternity). So Homer tried many jobs but none of them worked out (one job offer turned out to be a scam). After many of Homer and Marge's newly purchased baby supplies and Marge's wedding ring are repossessed, Homer decides to leave and find a job, in order to provide for Marge and his unborn son Bart... Marge is brought to tears by Homer's absence. In a parody of Raising Arizona, Homer leaves a letter to a sleeping Marge describing the above. However, even in sorrow, Homer still winds up irritating Patty, who complains for Homer to "not scratch the pen so loud".
Homer gets a job at a Gulp 'n' Blow taco restaurant, where Patty and Selma find him, after nearly choking on a taco filled with hair. Patty, who has absolute hatred for Homer, insists that they remain silent about it to Marge, simply to let her find him by "reading about it in the Society Pages". But Selma, feeling sorry for Marge and some pity for Homer, plans to tell Marge the truth. Marge, now well into her third trimester of pregnancy, finds Homer and convinces him to come back home with her. Homer feels ashamed and unworthy to be Marge's husband as he is not able to afford an appropriate wedding ring, but Marge tells him any ring is fine, so long as it is from him. Homer plans to apply for a job at the Nuclear Power Plant once more, this time marching into Mr. Burns' office and telling Burns dramatically that he will be the perfect spineless employee. Burns is so impressed that he hires Homer on the spot. Homer, glad that he has this well-paying job and that only "This could only happen in America" while skipping with joy is able to now buy back the repossessed wedding ring and baby items.
When Homer returns to Marge's house, he discovers she has gone into labor and is already at the hospital. Marge's mother Jacqueline offers to take Homer to the hospital (on the condition he never calls her "mother" again). Homer arrives shortly before she gives birth, where Patty snipes at Homer, saying he doesn't belong in the delivery room. Sick of constantly being bullied and belittled by Patty, Homer angrily tells Patty to shut up, then Patty insults him again ("Hey listen, fat boy!"). Then, in a rare fit of passionate rage, he angrily snaps at Patty ("No, YOU listen!"), demanding respect with such verbal force that it actually intimidates Patty into silence. He then turns to Marge, telling her of his success at finding a job. The rest of the delivery goes smoothly, except for one minor incident ("Homer, for God's sake, let the doctor deliver the baby!"). After the baby is born, Homer and Marge choose to name him Bart. Bart takes Homer's cigarette lighter and lights his tie on fire. Homer quickly dips the tie into a glass of water, gets mad at Bart ("Why you little--!!") and tells Marge that he did it on purpose, but Marge tells Homer that how could Bart do that as he is just ten minutes old.
After Homer finishes telling his flashback story, he tells Bart that the day he was born, Homer received the best gift a man could get and says he and marge was blessed twice more with Lisa and Maggie. Marge arrives home with the news that she is not pregnant, to which they are relieved at, and they are grateful.