S7E5: Lisa the Vegetarian

In "The Simpsons" Season 7, Episode 5, titled "Lisa the Vegetarian," Lisa decides to become a vegetarian after a trip to a petting zoo where she bonds with a lamb. Her new dietary choice isn't exactly embraced by her family or the town, leading to a series of unfortunate events, including a rather disastrous barbecue at the Simpsons' house. After being ridiculed at school and causing chaos at Homer's BBQ by ruining the roast pig, Lisa runs away in frustration. She eventually ends up at the Kwik-E-Mart where she meets Apu, who introduces her to Paul and Linda McCartney. The McCartneys explain to Lisa how they manage their vegetarian lifestyle and encourage her to stick with her beliefs without being preachy. Inspired by their advice, Lisa returns home and apologizes to Homer. The episode wraps up with Homer also apologizing, acknowledging that they can respect each other's choices. They reconcile over a veggie meal, and peace returns to the Simpson household — at least until the next episode's shenanigans kick in.