Clarisse is an abnormal person in the society of Fahrenheit 451. She wants to have real relationships with people instead of focusing on advertising and television, and she is more perceptive than most. When she meets Montag, her ideas strike him as strange, but he finds her fascinating because she triggers his own individualism. Her reaction to the world, where life is without value and where people destroy things for catharsis, is to try and understand it from within without being consumed by it:
"They believed in responsibility, my uncle says. Do you know, I'm responsible. I was spanked when I needed it, years ago. And I do all the shopping and house-cleaning by hand.
"But most of all," she said, "I like to watch people. Sometimes I ride the subway all day and look at them and listen to them."
(Bradbury, Fahrenheit 451, Google Books)
By examining the world and analyzing it based on what she thinks culture should really be like, instead of what it has been forced into by the government, Clarisse has a far more objective worldview than most people. She is able to see the humor in stretched billboards and repetitive conversations where most people would think nothing unusual. Sadly, her non-conformity is noticed by the government and she is (probably) killed to keep from influencing others.