Clarisse McLellan, the neighbor, acts as a doppelganger to Guy Montag. I say this because they both are very full of life compared to most of their society. “You’re one of the few who put up with me. That’s why I think it’s so strange you’re a fireman, it just doesn’t seem right for you, somehow.” said Clarisse on page 23. She realizes at an early stage in the book that he is not like the others, he is more like her and she wants to help him realize the truths of life.
Here are some examples of doppelgangers to better your understanding of them (granted James and Dave Franco are brothers they still like very much alike.)
Robby Hooker Fahrenheit 451 Blog 