Teen Titans 22 (July/Aug 69) contains two stories, the first of which concludes the Dimension X storyline, while the second finally gives an origin and identity for Wonder Girl, a good four years after the character was introduced.
Adams and Cardy pick up the lead story from the end of the previous issue. Speedy and Wonder Girl are on Earth, while Kid Flash and Robin are trapped with the aliens in Dimension X. Speedy and Wonder Girl turn over the Fat Man to the police, but have no luck in trying to figure out how to operate the transporter machine to reach the other dimension. The aliens try to kill them by sending a beast through, but that doesn't work.
The aliens send Robin and Kid Flash through a dimensional gate, claiming to be sending them to Earth, although they wind up in a different realm. Robin realizes that the aliens really want to see if the humans can see and interact with this realm, whose existence they only suspect, but Kid Flash falls for their ploy, and reveals that it does exist.
As it turns out, both pairs of heroes wind up heading back into the in between realm, and the aliens pursue them. An energy creature, the only form of life in that realm, gets very impressed by Speedy, who is busy firing arrows at the aliens. The energy being forms himself into an archer, and his energy arrows are able to hold back the aliens. The Titans leave for Earth, as the energy archer promises to prevent the aliens from ever traversing the dimensional barrier again.
The second story in the issue is by Marv Wolfman, Gil Kane and Cardy, and centres on Wonder Girl. She has been feeling weak, and is not sure of the reason why. This leads to her explaining to the rest of the team that she is not an Amazon, like Wonder Woman, but a human girl, from the United States.
Wonder Woman rescued her from a burning building when she was an infant. There was no sign of her parents, and nothing to establish her identity.
Wonder Woman brought her to Paradise Island, and named her Donna Troy. Hippolyta raised her as if she were another daughter, but Donna was never able to live up to the Amazons. Paula Von Gunther used the Purplle Healing Ray to alter Donna's body, and give her the same powers as Wonder Woman. That part of the origin was rarely referred to.
As the story continues, Donna moves into an apartment with Sharon Tracy. Sharon would appear again over the years, but very rarely. Wonder Girl gets a message from Hippolyta, explaining that her weakness had been caused by accidental feedback from the Purple Healing Ray.
As the story ends, Donna decides to get a new costume and hairstyle. They are both huge improvements. It's funny, Wonder Girl's new costume is not very much like Wonder Woman's outfit, maintaining only the stars, really. But it works very well despite that.