Plot
Leo Borlock, a teenager in Mica, Arizona, wears a porcupine tie in remembrance of his late father. On each birthday, he receives a new porcupine tie from an unknown person. In high school, Leo plays trumpet in the marching band and helps his friend Kevin Singh, a member of the A.V. club, host an interview show. The free-spirited Stargirl Caraway makes an impression on Leo and later performs for their losing football team, the Mudfrogs. Kevin and Leo invite her onto their show, but she politely declines.
Stargirl becomes a good luck charm for the football team and begins hanging out with Leo and tries to get him to come out of his shell. Archie, the owner of the local paleontologist camp, tells Leo everything about Stargirl, who also learned about Leo through Archie. Later, Stargirl tries out for the Speech regionals against Kevin and wins with an unusual speech on rats before denying any knowledge of returning a bike to a boy who was in the hospital. Stargirl and Leo kiss for the first time and begin dating.
During the big game, Stargirl rides with an injured opposing player to the hospital, upsetting everyone, leading to the team's loss and causing Stargirl to lose her popularity. Leo's friends are upset, but they forgive him. The situation escalates after an interview of Stargirl on Kevin's show goes horribly wrong. Leo suggests that she act like everyone else, much to her consternation, she starts calling herself Susan and wearing clothes like those of her classmates. At the Speech regionals, Leo asks Stargirl to the Winter Dance, and she accepts. She is about to give a speech on internet privacy, but shifts to a speech on flowers, which wins her first place. Although it is the very first trophy won at the school, nobody pays attention to it. As he begins losing hope, Leo gets encouragement from his mother and Kevin.
Stargirl sends Leo her collection of records, a record player and an invite for a "big surprise" at the dance. When Leo arrives, Stargirl reveals her surprise: him singing in front of everyone. Leo reluctantly gets up and performs his and his father's favorite song, "Just What I Needed", leading everyone to dance in the courtyard. Afterwards, Leo discovers that Stargirl has moved away, but even after graduating high school, Leo never forgets what Stargirl did for him.
