The Simpson family are freezing inside their house. Bart and Lisa, searching for items to feed the fire, discover a box containing a degree belonging to Marge from Springfield University. Homer and Marge look shocked to find it, and claim it was from their dating years. Lisa does some calculations and realizes that, because Bart is 10, and Homer and Marge are in their mid-to-late thirties, Bart must have been born later in their parents' relationship than they thought. Marge and Homer proceed to describe one of the darker points of their relationship, the 1990s.
In the flashback, Homer and Marge are happily dating, living together in an apartment. Marge is an avid reader, and Homer is part of an R&B group alongside Lenny, Carl, and Officer Lou. One morning, Marge wakes up to find out she had been accepted into Springfield University, but is shocked to learn of the high cost of tuition. Homer, taking pity on Marge, gives up his dream of becoming a musician and instead decides to work at his father's popular laser tag warehouse in order to pay for it, where he is abused by the children. At Springfield University, Marge is impressed with her surroundings and with the radically feminist revisionist history professor Stefane August, despite Homer's disapproval.
Marge soon begins to admire August, and realizes she has feelings for him. August begins manipulating Marge by telling her Homer is a simple "townie" who would not appreciate her intellect. A shocked Homer arrives and catches the two together. In his anger, he reforms his R&B group with a new sound called "grunge," which Homer explains is an acronym for "Guitar Rock Utilizing Nihilist Grunge Energy." His band is renamed to "Sadgasm" and they sing a song Homer calls "Politically Incorrect", listed in the episode's credits as "Kisses are Dirt". An angry Marge and Homer soon call their relationship quits, and Marge leaves to go with Professor August.
Homer goes on to perform a new song, called "Shave Me" (based on "Rape Me" by Nirvana), which causes him to become so famous that "Weird Al" Yankovic parodies his song calling it "Brain Freeze". Marge finds Homer's music unnerving. Marge and August share their first kiss. When running onto the beach, August reveals he and Marge have very different views on marriage. After the two argue, Marge breaks up with him, breaking his heart. A miserable Marge watches television and is surprised to see Homer made a song dedicated to her, called "Margerine" (based on "Glycerine" by Bush), about what she did to Homer. A special news report with Kurt Loder interrupts, revealing Sadgasm had broken up and Homer is holed up in his mansion, miserable. Arriving there, Marge thinks Homer had been doing drugs and soon begins caring for him. It turns out the needles were insulin for his diabetes. The two soon re-unite.