"I Love Lisa" is the fifteenth episode of Season 4.
On Valentine's Day, Lisa takes pity on Ralph and gives him a valentine when she sees that he hasn't received any. But Ralph reads too much into Lisa's gesture and, much to Lisa's dismay, relentlessly pursues her.
The episode begins on Valentine's Day, with KBBL Radio DJ Marty playing 'Monster Mash' on the radio accidentally while trying to pass it off as a deliberate choice. At school, Lisa's class begins constructing paper mailboxes for all the cards they are about to receive. When Ralph doesn't get any cards and begins to sob, Lisa hastily gives him a card out of sympathy. Ralph immediately cheers up, and develops a crush on his classmate.
Ralph begins to follow Lisa around, following her home and discussing his medical maladies. Lisa tries to escape the situation and let him down gently, but Ralph, with the encouragement of his father to keep trying, doesn't understand and uses his position as the police chief's son to get her tickets to Krusty's upcoming 29th Anniversary Special, as well as a leading part for himself in a President's Day Pageant as George Washington (beating out the school's best actor, Rex) with Lisa also starring as Martha Washington, George's wife. This of course doesn't settle in well with Rex and he accuses Miss Hoover of being bought out. Though Ms. Hoover claims it fair, it's soon revealed that she was blackmailed by Ralph's father.
With Homer having convinced Lisa that nothing can go wrong at Krusty's show, and Bart pointing out how great it is, Lisa and Ralph go together. On live air, Krusty begins interviewing audience members, and the excited Ralph takes the opportunity to declare that Lisa is the love of his life and that he intends to marry her. Angry, Lisa begins to shout in front of everybody at Ralph that they are not in any relationship, and she never liked him, and that the only reason she gave him a Valentine card was because she felt sorry for him. Bart replays the incident for Lisa later on videotape, showing Lisa how she broke his heart and humiliated him on National Television, and Lisa feels terrible.
When the humiliated Ralph tells his father what happened, Wiggum is furious, taking advantage to smash out Homer's tail light at a traffic stop. However the angry Homer tells him that one day honest citizens will rise up against corrupt cops and Wiggum is quickly at a loss.
The day of the play finally arrives and Lisa tries to take the opportunity to apologize to Ralph, however he refuses to listen, determined to play his part just the same. In the meantime, Bart wreaks havoc, making his butt look like Richard Nixon and then mooning the other students. Mrs Hoover stops him and reminds him that he is to play Abraham Lincoln's assassin, John Wilkes Booth, not act like a maniac.
The play begins with one group of students singing about the lesser-known U.S. Presidents. The assassination of Abraham Lincoln (played by Milhouse) is then played out. Bart models his performance on The Terminator rather than on the real Booth ("Hasta la vista, Abey!") and an annoyed Miss Hoover drags Bart off the stage in disgust. The main feature however is a re-telling of George Washington's life story. At first, Lisa is convinced that Ralph has forgotten his lines, or intends to humiliate her as she did him. However he gives a touching and emotional performance that affects everybody in the audience, inspiring the bully trio to learn more of their founding fathers and making Groundskeeper Willie tearful.
The play ends with an animatronic Mount Rushmore singing one of the stanzas of "America The Beautiful", as well as giving away final stage announcements to the audience to buy orange juice.
Afterward, Ralph signs autographs and greets well-wishers. Lisa also approaches, and gives him a new card, reading "Let's bee [be] friends." Ralph laughs at the joke and thanks Lisa, the two making up. Chief Wiggum watches Ralph and Lisa sitting together on the swings while listening to radio and the episode finishes as it began... with Marty accidentally playing 'Monster Mash'.
Krusty the Clown Show Characters, Locations and Key Episodes