Donna Hinckley Stacey Troy has had as many different origins as any other DC hero, but unlike the rest she currently remembers all of them.
In her original origin, Donna was an orphan (her parents were killed in a fire) who had been saved by Wonder Woman and taken to Paradise Island, where the Amazons used the mysterious Purple Ray to grant her Amazonian powers. Donna then joined several other junior heroes to form their own super-team, the Teen Titans—she took the name "Wonder Girl," which until she adopted the alias “Donna Troy,” was her only name.
As Wonder Girl, Donna became a well-known figure in the DC Universe. Many years later, she was recast as Troia, champion of the mythic Titans. She later gave up her powers to become human, marry, and have a son, but years later (and after losing her husband and son in a car accident), regretted her decision. When the Titans refused to take her back, Donna became a Darkstar instead.
After leaving that group, Donna discovered she was actually a magical duplicate of Diana, the true Wonder Woman, and regained her powers before being acknowledged by Queen Hippolyta as a true Amazon princess. Since then Donna has discovered the existence of the Multiverse and the fact that she is the only person to remember all of her changing origins. As such, she has become the key to nurturing and protecting the new Multiverse.