The episode begins with Homer and a six-year-old Bart in early 2012, lying down on the grass, as Bart asks things about nature to his father, only for Homer to ask him why he left his toy cars on the stairs, resulting in a terrible fall. The family decides to take Bart to Grandpa's house to leave him away from Homer. As Bart asks Grandpa to play with toy cars, he remembers about an old car he had bought brand new in 1954 and forgot about. Bart asks if he can sit in it, but Grandpa reveals that Bart can actually drive it.
The episode fast-forwards two years to the future in late 2013, with Bart still driving Grandpa's car, late for his reading class. Professor Frink tries to teach him without much success, and discovers that Lisa, who is two years younger, can read almost perfectly. Later, Lisa paints a boat on the sea, to which Marge decides to place over the couch. Bart reveals that he made a painting on the entire kitchen. While Homer is painting the walls and furniture to its original color, Bart tries to impress Lisa by driving Homer's car, only to crash it through the kitchen wall, almost hitting his father. Homer and Marge decide to go to a psychologist to see why their son is such a troublemaker. She says that it is because of Homer's lack of attention for him and that they should go camping together. But instead of taking the boy camping, Homer takes him to an inn to watch ice hockey, making Bart sad. Back at home, he discovers that Lisa is the student of the month at Springfield Elementary, even though she has only been there for a month, while Bart has been there for two years and has not won anything. Homer tries to reconcile with him by saying he loves both of them the same amount: 40%. Bart makes a bumper sticker for Homer's car, but he ignores it because there is no more space for stickers in his bumper.
The episode fast-forwards to Bart's 12th birthday in 2017, where Lisa gets the news that she is student of the month at Springfield Elementary for 48 consecutive months. Bart gets angry because his sister can overshadow him even at his birthday party, so he decides to go skateboarding with Milhouse. They decide to break street lamps, but Milhouse gets arrested and taken to juvenile detention while Bart was hiding at the retirement home, where Grandpa gives him a BMX.
Three years later in 2020, Bart, now 15, is good at doing stunts with his bike. Marge and Lisa go to a camp together, leaving Homer and Bart alone. Marge mentions that this could be Homer's last chance to have a close relationship with Bart, only for them to talk a few seconds, with Homer leaving him home alone once again. Bart throws a party at their home only to find Homer high on marijuana, where he reveals that he was exactly like Bart, but when he was born, this meant he was not a child anymore. They hug each other, but their moment is ruined when Homer mentions that he will not go anywhere or do anything.
Bart goes to Grandpa's grave, where he gets the idea of going to a BMX competition, where he would never be overshadowed by Lisa. At one of his stunts, however, he gets distracted by Lisa's shadow, hits the ground too hard and blacks out, only to discover that he was brought back to consciousness by Lisa, who is then proclaimed as a hero, making him angry. In 2024, Bart decides to make caricatures at the port, where he is invited to Milhouse's graduation party. He is reluctant to go because his sister is graduating the same year as them, but he decides to go anyway. At the party, Milhouse's parents fight in front of him, so Lisa tries to make him happy by saying he's "cuter then ever", resulting in Milhouse replying that she's the best thing at that party. Bart gets irate that he is always the second best Simpson in everything, but Lisa confronts him by saying she's tired of him blaming her for every setback in his life, and that he is a good artist, even though he never does anything with his talent. Bart decides to take his sister's rage as an advice.
Two years later in 2026, Bart opens a bike customization shop, where he is surprised by Nelson, who wants to give all the lunch money he stole at school back, giving Bart $5,000. He is also surprised to see that Lisa and Nelson are dating (again). He shows them a giant painting on a wall, showing various moments through his life. Lisa realizes that she is not on any part of the painting, so Bart lowers one of the shop's doors to show her a giant painting made in her homage as one of his favorite sisters. Nelson discovers that El Barto is actually Bart.
Back on the lawn in 2032, Homer finally answers Bart's (now an adult) questions in detail (among other things, the grass they're lying on is green because it's artificial) and finishes by advising his son to pretend to be on the phone if anyone tries to ask him for something—which he immediately puts into action as Bart tries to ask another question as the next questions play through the credits.