The Pebble Wagon
The pebble wagon symbolizes Stargirl's happiness. She uses that wagon as a personalized happiness meter and regulates the number of pebbles being thrown into it. if there are only two, she's not having the best day. When she's around Leo, that wagon is almost filled to the brim. This pebble wagon never reflects what Stargirl projects externally, but how she feels internally. Stargirl never shows sadness, anger or ridicule. She always shows compassion and kindness, so in a way, the pebble wagon is an indirect way for her to express her disheartenment. Throughout the book, Leo notices the fluctuations of the pebble wagon which is how the reader know's Stargirl's mood, otherwise Stargirl would be portrayed as a happy character throughout the whole book.
Cinnamon the Rat
Cinnamon is Stargirl's rat and faithful companion. We can tell that throughout the book, the one character that stays consistent in Stargirl's life is this rat. Throughout the book, Stargirl joins a cheerleading team, meets Leo, and heightens her popularity status at school. As the book takes a turn, she starts the lose friend after friend, including Leo, because of the public shunning she gets from the whole school. However, the one companion that stays with her is her rat. This rat symbolizes her identity and her individuality. No matter how much she experiences, no matter what actions she performs, her rat is always there, a rat that expresses the definition of "her".
The Ukulele
The Ukulele represents the freedom of expression. An expression is an important component of the theme of individuality, and it is Stargirl's method of spreading happiness and joy throughout the school. She never once fails to sing Happy Birthday to a fellow student, and always has it on hand, strumming and giving sound to the world that she feels needs to be more colorful and plentiful. She's adding sound to a world where everything is black and white, slowly turning everything to color.
A Cactus Flower
The cactus flower is a representation of the environment Stargirl is in. Stargirl lives in an area where there are desert, bones, and dust. It's a musty, dry environment with no color or personality. That is until the symbol of a cactus flower arises. Throughout the book, Leo does refer to her as the cactus flower, the small bit of color in the drudgy environment surrounding them. She is the physical embodiment of life at it's fullest, just as the cactus flower is the only symbol of life in the desert.
Stargirl
Stargirl's name can be taken as a symbol itself. It portrays that she is not like the "normal" person, and she chooses to express herself more externally than internally. Even her name is unique and reflects upon her enjoyment to look at the night stars. Her name is how she wants to reflect to other people, rather than using her own name 'Susan', something that has no representation or meaning.
Caraway (Stargirl's last name)
Stargirl's last name, reminiscent of that of the narrator of The Great Gatsby, Nick Carraway, is significant because it reveals Stargirl as someone without cares. Stargirl has literally given her cares away by spending all of her time on others - sending them notes and leaving anonymous gifts for them.
