Cassandra "Cassie" Sandsmark, known as Wonder Girl, is a prominent superheroine in DC Comics, serving as a sidekick and protégé to Wonder Woman. Created by writer and artist John Byrne, she made her debut as Cassie Sandsmark in Wonder Woman (vol. 2) #105 in January 1996, with her first appearance in costume as Wonder Girl occurring shortly thereafter in issue #111. The teenage daughter of archaeologist Helena Sandsmark, Cassie spent much of her early life surrounded by ancient artifacts, fostering a deep admiration for Wonder Woman and a desire to emulate her heroic ideals.
Initially, Cassie gained temporary superhuman abilities by secretly borrowing magical Amazonian relics, including the Sandals of Hermes for flight and the Gauntlets of Atlas for enhanced strength, allowing her to assist Wonder Woman in battles against threats like Doomsday clones and Decay. Impressed by her courage, Zeus later bestowed genuine powers upon her, granting super strength, speed, durability, and flight independently of artifacts. Revelations in her backstory established her demigod heritage: originally depicted as the direct daughter of Zeus, this was retconned in the New 52 era to make her the granddaughter of Zeus through her father, the demigod Lennox, solidifying her ties to the Olympian pantheon and Wonder Woman's extended family.
Over the years, Cassie has undergone significant character development, evolving from an impulsive adolescent into a mature leader. She co-founded and became a key member of Young Justice alongside peers like Robin, Impulse, and Superboy, with whom she developed a romantic relationship. Transitioning to the Teen Titans, she assumed leadership roles during turbulent periods, including following the deaths and resurrections of teammates amid events like Infinite Crisis. Influenced at times by gods such as Ares, who temporarily amplified her powers, and grappling with artifacts like the dangerous Silent Armor in certain continuities, Cassie has consistently demonstrated resilience, proving herself a worthy bearer of the Wonder Girl mantle through her dedication to justice and personal growth.