Lisa debates becoming a vegetarian after a trip to the zoo makes her think about where her food comes from. But being surrounded by meat eaters like Homer, she wonders if she can follow through. She later crosses paths with vegan Kwik-E-Mart attendant Apu, who shows her his secret roof garden and introduces her to Paul and Linda McCartney. The musical couple shares their history with animal rights and discusses Lisa's decision to pursue a vegetarian lifestyle.