- Things started in the very beginning. William Moulton Marston created Wonder Girl as a young Wonder Woman to tell her adventures during her young age (which would be more appealing for kids). She once called Hippolyta "Mother". That implies two things: that this character is Wonder Woman, and that those adventures take place in the past. But it was the 1950s and '60s, and nobody paid much attention to details. When this character had team-ups with Wonder Woman first, and with other superhero sidekicks set in the present time, things got out of control. So, what the hey. They named the character Wonder Girl, and Neal Adams gave her an Origin Story. She was Donna Troy, an orphan rescued by Wonder Woman from a building on fire, and taken to Paradise Island. She was raised by Hippolyta, and became Wonder Woman's adoptive sister. She received powers similar to those of Wonder Woman from the all-purpose purple ray. And everything was fine... for some time.
- The Teen Titans were relaunched in the 1980s by Marv Wolfman and George Pérez. They wrote the story Who Is Donna Troy?, which expanded the origin story, and still made perfect sense. But then, they screw it with Crisis on Infinite Earths. The DC Universe was rebooted, and Wonder Woman was redesigned as a rookie who had just arrived to the world of men. The Teen Titans, who were such a big success, were not rebooted. But then, what about Donna's origin? Wonder Woman couldn't have saved her. No Wonder Woman means no Paradise Island and no purple ray, so what about Donna's powers? It had to be fixed with a new story, Who Is Wonder Girl?. The fire rescue is kept, but now she was rescued by the Titans of Myth, who rescued doomed children at several planets, turned them into demigods, and then returned them home with fake memories. No good explanation was given for the name "Wonder Girl" when there was no Wonder Woman, though. She took a new suit and changed her name to Troia.
- And now what? Now... yet another origin story. Now, Donna was a mirror reflection of Wonder Woman brought to life to be her friend, and got kidnapped by Dark Angel, who (thinking that she had kidnapped the real Wonder Woman) cursed her to live several traumatic lives. She is saved by Flash and Wonder Woman, and re-adopted by Hippolyta, but with a slight problem: She is not the "real" Donna, but a new one re-created from the memories of Wally and Diana. And then, she was killed by a rogue Superman robot. The end? Hell, no.
- She was brought back in a prelude to Infinite Crisis. She has now been adopted by the Titans of Myth as one of their own, the goddess of the moon, with fake memories (again!). If we can avoid talking about the part about the Donnas of the multiverse, so much the better. Her origin was changed once again: We keep the part of Dark Angel, but now she was kept frozen for a time, released, and adopted by the Amazons. Now, in the absence of Diana, she became the new Wonder Woman.
- All the DC universe was rebooted with New 52. Initially, Donna was absent, and there was another Wonder Girl: Cassandra Sandsmark, who had been a second Wonder Girl in previous years, when Donna had already given up that identity. She was finally included in Wonder Woman #37, created by magic, as an alternative to the throne of the island. Without all the previous baggage, things made sense, but this version of the character was pretty reviled, so DC fucked things up again! The Titans were incorporated again, and it was stated that there was a team called the Teen Titans (consisting of Donna, Dick Grayson, Roy Harper, Garth, Lilith Clay, Hawk and Dove and later also Wally West (who stayed forgotten after the story)), erased from public memory by Mr. Twister. But one of the members of this team was a young Donna Troy, who was Wonder Girl. Which does not make sense, since she was created recently, and as an adult.
- Then came DC Rebirth, which had Donna state that she was an orphan raised by the Amazons. This is obviously in direct conflict with her origin in the New 52, but hey, whatever, right? Well, it's later revealed that she is still the New 52 clay Donna Troy, and her false memories of being an orphan raised by the Amazons were given to her by the Amazons to give her a fresh start as a superhero. How this even works, with the New 52 Amazons being revealed to be an illusion in Wonder Woman (Rebirth) remains to be seen, as well as the fact that, in the Rebirth timeline, Donna was still Wonder Girl, which couldn't have been possible with the clay Donna, who's about a year old, if you wanna push it. Not only that, but Wally West is established as having been protected from the numerous memory-altering hijinks going on, so it's doubtful that what the Amazons did could affect him, and he remembers Donna being Wonder Girl!
Continuity Snarl / Donna Troy