The porcupine necktie is Leo's connection to his past. When his family was preparing to move from Pennsylvania to Arizona, Leo's beloved Uncle Phil, who was fond of porcupine neckties, came to bid the family farewell. In a dramatic gesture, he gives his porcupine necktie to Leo. Leo has always cherished porcupine neckties and his connection to it exists as part of his connection to his Uncle and his past.
Some time after his fourteenth birthday, Leo finds a package on his doorstep and it is a porcupine necktie. As the narrative progresses, it becomes clear that Stargirl gave him the tie after reading about his biography in the newspaper that claimed that he collects the unique type of tie. In truly symmetric fashion, the ending of the story reveals that before his last birthday, Leo received another porcupine necktie. It is here in which one sees that Leo's connection to the porcupine necktie is reflective of both his past with Uncle Phil and also his past with Stargirl, something that will always color his present and future, even if they are no longer together. The porcupine necktie reflects Leo's everlasting connection to Stargirl.