Leo Borlock is an average student at Mica High School. He gets decent grades, is a member of the school's marching band and has always been content flying under the radar. But all that changes when he meets Stargirl Caraway, a confident and colorful new student with a penchant for the ukulele, who stands out in a crowd. She is kind, finds magic in the mundane and touches the lives of others with the simplest of gestures. Her eccentricities and infectious personality charm Leo and the student body, and she quickly goes from being ignored and ridiculed to accepted and praised, then back again, sending Leo on a rollercoaster ride of emotions.

Stan is an ageing sheep farmer who's at odds with life and out of hope. During a meteor storm a mysterious female alien arrives on his farm, she appears to be lost. As they attempt to understand each other a bond is formed and Stan teaches Voyager about what it is to be human. Their fate and Stan's is sealed when the StarGirl confesses her real reason for visiting Earth.

Courtney Whitmore, a smart, athletic and above all else kind girl, discovers her step-father has a secret: he used to be the sidekick to a superhero. "Borrowing" the long-lost hero’s cosmic staff, she becomes the unlikely inspiration for an entirely new generation of superheroes.

When Stargirl's mother is hired as the costume designer on a movie, they relocate to L.A., where Stargirl quickly becomes involved with an eclectic assortment of characters.

A mysterious young woman materializes in the middle of the southwestern desert, where each step teaches her about her new world and her new body. As she assumes her new life, she discovers she has a twin with whom she shares more than just an outward appearance.