Lisa Simpson is the middle daughter of Homer and Marge Simpson. At eight years she is the most intelligent, committed and idealistic member of her family and probably of all Springfield. She's always been an advocate for animal rights and is strongly commited to the environment by combating pollution and climate change, something that many times made her confront her less conscientious neighbors.
In addition, Lisa also has a sharp sense of irony she did not hesitate in using when her father thought he had foretold the Armageddon in the holy scriptures. Lisa's response to this apocalyptic revelation was that "the world's not coming to an end! Yet... A hundred years, global warming, we're goners!"