It's important to start this entry with the answer to the question “who is Donna Troy?” which is “we don't really know and nothing I say here is going to help you understand.” To start, writers of the ‘60s Teen Titans series had possibly ignored or not realized that while all the other sidekicks they used in Teen Titans had established backgrounds no Wonder Girl had ever been officially introduced or explained. A teen version of Wonder Woman called Wonder Girl had been making appearances in Superboy style stories until one issue where she showed up as a separate entity. Her first appearance in Teen Titans was to arrive on the Titans doorstep and act like she had always existed. The original assumption was that Wonder Girl was merely the younger sister of Wonder Woman. In the following decades she's gone on to have possibly the most needlessly convoluted origin story ever and to be dubbed “most complicated” by people who have read X-Men comics.

The first retcon of Donna Troy was with good intentions — she'd simply never been given an origin story, so it was explained that Wonder Woman had saved her from a fire then pelted her with purple rays on Amazon Island to give her powers. After that, a change in Wonder Woman’s origin made it impossible for her to have saved an orphan from a fire at the time, so Dick Grayson, that absolute schmuck, decided he needed to start investigating the matter, which we all to this day regret him doing. He discovered the original story to be false, and Donna happened to be the victim of a good old-fashioned child trafficking racket. OK! Easy enough, but then in New Teen Titans #50-54, the fire plot gets brought back, and we discover it was actually the Titan (not Teen Titan but Greek Titan) Rhea that had saved Donna, and gave her and 11 other orphans superpowers to make them the Titan Seeds, which does not sound okay in the slightest. One of them goes rogue and starts killing the others, and Donna Troy changes her name to Troia. After that, it turns out that Donna had been created as an age-appropriate playmate for Diana who then was mistaken for Diana and cursed to live out painful traumas again and again for eternity. Later, during another retcon, we discover again none of this is true because it's all true because retcons.

All that said, it’s pretty difficult to say who Donna Troy is at any given point in time. If you ever find yourself asking a seasoned comic fan and they gruffly mumble “she’s just — a clone. A clone! Turn back now!” before chugging out of a flask and passing out in public, go ahead and believe them because we’ve pretty much universally decided to go with “clone” at this point to save ourselves the struggle.