THE SIMPSONS Season 12 Episode 4 : Lisa the Tree Hugger
Bart wants the new Gamestation 256, so he tries to get a job to earn the money, but his job as a menu boy causes a great deal of paper litter to be strewn about the city making Lisa lament the plight of the trees. Then Lisa falls for a meat protester, which inspires her to join their environmental protection group. Later, when an old redwood tree is danger of being cut down, she begins living in the tree, but her desire to return home becomes to great and she leaves for just a little while. However it's too late because when she returns the next morning the tree has come down. During the night the tree was struck by lightning and the city thinks that Lisa is dead.