Unlike other heroes, the event that led to Courtney Whitmore becoming a hero wasn't tragedy. Instead, it was the breakup of her parent's marriage and her mother's remarriage to a man named Pat Dugan. She was miserable in her new life and blamed her stepfather. In Pat's belongings, she stumbled across the gear of the hero, 'The Star-Spangled Kid' and realized that Pat had once been the adult sidekick of a teenage hero. To make a mockery of Pat, she decided to wear that gear to a school dance. However, detecting someone wearing the Kid's gear, one of Kid's old enemies thought someone had taken up as the new Star-Spangled Kid and attacked the dance. Her stepfather came to Courtney's aid in a suit of mechanized battle armor he had been secretly working on and the two defeated this old foe.

Exhilarated by the battle, Courtney decided she wanted to continue on as a hero. Seeing how well she'd handled herself and how it could help them grow closer as father and daughter, Pat agreed. However, there was one condition: He would have to fight alongside her as her guardian. Amused that he would now be her sidekick, Courtney agreed and took on the shorter heroic name, 'Stargirl'.

Courtney Whitmore is an attractive and cheerful teenage girl, adoring the life she leads as a hero. Due to her young age, it is unsurprising that she can sometimes be naive about how the world works. The Cosmic Staff she wields grants her the ability to fly and can manipulate energy on a large scale, creating energy blasts and defensive shields.