"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 gets no cards and begins to cry, Lisa hastily gives him a card out of sympathy. Ralph immediately cheers up, and develops a romantic interest in his classmate.
Ralph begins to annoy Lisa at every turn, following her home and discussing his medical maladies. Lisa tries to escape the situation and let him down gently, but Ralph 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, Ralph's "wife." This doesn't settle in well with Rex as he had hoped to play alongside Lisa as Washington in the pageant and instead will portray a servant. Though Ms. Hoover claims it fair, it's soon revealed that she was blackmailed by Ralph's father and of which Rex suspects.
With Homer having convinced Lisa that nothing can go wrong at Krusty's show, Lisa and Ralph go together. On live air, Krusty begins interviewing audience members, and Ralph takes the opportunity to declare that Lisa is the love of his life and that he intends to marry her. Angry, Lisa tells Ralph they are not in any relationship, and she never liked him, and that the only reason she gave him a valentine was because she felt sorry for him. Bart replays the incident for Lisa later on videotape, and applauds her for embarrassing him on National Television. However after seeing how hurt and humiliated Ralph is, Lisa feels guilty over how badly she treated him.
An upset Ralph bemoans his situation to his father, but the only way Chief Wiggum can respond is to break out Homer's tail light after a traffic stop. However, Wiggum is quickly at a loss when Homer says that one day honest citizens will rise up against corrupt cops.
The night of the President's Day Pageant finally arrives and Lisa tries to take the opportunity to apologize to Ralph, however he refuses to listen. Bart wreaks havoc as usual, making his butt to look like Richard Nixon and then mooning the other students in the play. One group of students sings about the lesser-known U.S. Presidents, and Bart plays John Wilkes Booth assassinating Abraham Lincoln (played by Milhouse). Bart, however, is still in prank mode, and models his performance on The Terminator rather than on the real Booth ("Hasta la vista, Abey!") while scaring away the students. Not impressed by his shenanigans, an annoyed Miss Hoover drags Bart off the stage in disgust. The main feature is a re-telling of George Washington's life story, and, surprisingly, Ralph proves to be a very good actor in the role of George Washington, inspiring the school bullies to study American history. (Rex ends up playing George Washington's servant, and has just one speaking line.) Ralph's performance even causes Groundskeeper Willie to start crying. 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.
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 his son 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