“He's not like anybody I've ever met. He's like a riddle wrapped in an enigma wrapped in a vest. He sure is ugly, though. So why can't I stop staring at him? Oh no! I think I'm getting a crush on Nelson Muntz!”
―Lisa thinks about Nelson
"Lisa's Date with Density" is the seventh episode of Season 8 (originally going to be the first episode of Season 8 as produced in the same year as season 7).
After someone steals the Honda "H" off Superintendent Chalmers' car, Principal Skinner tries to track down the culprit. Nelson is the suspect and Lisa falls for his rebellious ways and soon develops a crush. It is now up to Lisa to change Nelson for the better actions of his persona. Meanwhile, Homer obtains a telemarketing machine, which drives the entire town bonkers.
At Springfield Elementary School, Superintendent Chalmers visits Principal Skinner to show off his newly purchased car – a 1979 Honda Accord – but becomes distraught when he discovers that the car's hood ornament has been stolen. Principal Skinner orders a locker-to-locker search, asking the students if they think it is funny that Superintendent Chalmers is at home crying like a girl - but they do. Regardless, it is soon determined that Nelson is the perpetrator, his locker is packed with a 'principal's ransom' of stolen property. As punishment, Nelson is forced to return the goods. Lisa questions Nelson as to why he always bullies other students, but Nelson responds by making fun of Lisa's fat bottom. Nelson then has to help Groundskeeper Willie with chores around the school campus as further punishment.
In music class, Lisa is caught looking out of the window at Nelson annoying Willie and is given detention by her music teacher Mr. Largo. While she is in detention, Nelson walks to the window and advises her on how to faster complete her punishment and once he walks off, she continues to watch him, and realizes that she has developed a crush on him.
Lisa lets Nelson understand how she feels about himself after attempting to pass him a love note in class, which resulted in Nelson seriously injuring Milhouse (Nelson thought that the note was from him). Lisa chooses to reform Nelson into a model student: She changes his appearance by taking him to the Wee Monsieur (where he is dressed in a sweater and slacks) and giving him a new haircut (Nelson states that he feels like a tool). The two later share a kiss during their date at the Springfield Observatory (this was Nelson's attempt to silence Lisa, but he found that he liked it).
However, the influence of Nelson's friends – Jimbo, Dolph and Kearney – proves to win out when they convince Nelson to throw spoiled coleslaw that they found behind the dumpster from Krusty Burger at Principal Skinner's house. Skinner immediately fingers the boys as suspects, and they run away. Nelson takes refuge with Lisa, claiming innocence. Lisa believes him, until Nelson finally lets the cat out of the bag, before realizing that Nelson has been lying to her, and thinks that they should end their relationship for their sakes, to the joy of the jealous Milhouse, who has had a longtime crush on her.
In the subplot, Chief Wiggum arrests a confidence trick scam artist for telemarketing fraud. Homer witnesses the takedown and sees the discarded autodialer in a nearby dumpster. Homer takes the autodialer to the Simpson house to use for telepanhandling.
Homer ends up annoying Springfield with his "Happy Dude" confidence trick scam, including Ned Flanders, who keeps answering the phone to hear the autodialer and Maude Flanders threatens to make Ned sleep outside on the lawn unless he unplugs the phone. This annoys Homer, and he orders the couple to shut up because other people are trying to sleep. Eventually, it is not long before Chief Wiggum catches Homer. Instead of confiscating the autodialer and taking Homer into custody, Wiggum gives Homer a citation and is asked to bring the autodialer to his court hearing. Homer does just that and is ordered to give apologies to everyone he scammed. He does so using a prerecorded message and the autodialer, and at the end of the message asks for more money.