http://en.wikipedia.org/wiki/Lisa_the_Vegetarian
“Lisa the Vegetarian” is the fifth episode of The Simpsons’ seventh season. It originally aired on the Fox network in the United States on October 15, 1995. In the episode, Lisa decides to stop eating meat after bonding with a lamb at a petting zoo. Her schoolmates and family members ridicule her for her beliefs, but with the help of Apu, Paul McCartney, and Linda McCartney, she commits to vegetarianism.
The Education of Lisa the Vegetarian
Sunklands 