In Fahrenheit 451, how is Clarisse's family different from the others in the neighborhood?
In contrast to the people of the futurist society, the family of Clarisse is more like the contemporary American families of the readers.
When Montag meets Clarisse oddly walking around outside in the evening unlike others in the neighborhood, she engages him in conversation. Strangely enough, Montag "saw himself in her eyes" and he feels comfortable because he is reminded of a time when he was a child and because the power went out, his mother lit a candle. For Montag it was "a brief hour of rediscovery...that space drew comfortably around" his mother and him.
Unlike their neighbors, Clarisse and her family live in this other time "of discovery" when people actually engage in conversation with one another and share feelings. As she and Montag walk toward her home, he is startled to see that all the lights are on, and he asks Clarisse "What's going on?"
"Oh, just my mother and father and uncle sitting around, talking. It's like being a pedestrian, only rarer. My uncle was arrested another time--did I tell you?--for being a pedestrian. Oh, we're most peculiar."
Montag then asks her what Clarisse and her family talk about; his question draws a laugh from the girl, who starts up her walk. Before going into her house, she turns to glance back at him with "wonder and curiosity." Clarisse asks Montag if he is happy, and he is startled by her question about emotion.
After he returns home, Montag ponders his odd encounter with this girl:
How rarely did other people's faces take of you and throw back to you your own expression, your own innermost trembling thought?
Certainly, the humanity and depth to Clarisse and her family have become obsolete in Montag's world.
Clarisse's family are one of the vanishing breed of individuals in the future society; her parents and relatives still remember the pre-book-ban world, and are generally dissatisfied with the new society. Clarisse learns most of her individualism from them, and is thus able to see past government indoctrination and the superficial satisfaction of TV.
When they reached her house all its lights were blazing.
"What's going on?" Montag had rarely seen that many house lights.
"Oh, just my mother and father and uncle sitting around, talking. It's like being a pedestrian, only rarer."
(Bradbury, Fahrenheit 451, Google Books)
Montag's surprise comes from his own typical life; he does not yet understand how unhealthy it is to sit and watch TV all the time, or why the TV shows are so empty of content. Instead, he equates TV, and shared TV watching, with normal societal interaction. The concept of "sitting around talking" is almost alien to him; he only converses on the job or while walking with someone. The strangeness of Clarisse's family, and his sudden desire to experience them, is one of the things that sets Montag on his path to individualism.