Don and Dawn Allen were the twin son and daughter of Barry and Iris Allen, who lived during the 30th century of Earth-One. Ed Moley and Joannie Swift were two non-powered individuals each tied to the lives of Johnny Chambers during the 20th century of Earth-Two.
Don and Dawn sought to honor their late father, who was the Flash, by adopting the alter egos of the Tornado Twins. Then, on a series of adventures, they seemingly upstaged the members from the Legion of Super-Heroes in futuristic costumes, before finally being revealed as the descendants of the Scarlet Speedster himself when the donned versions of Kid Flash's costume and confronted the Legion. Apparently, they were simply trying to promote the Flash Day commemoration, and so temporarily empowered themselves with the speed force. During their sole pre-Crisis appearance, their powers lapsed after this 24-hour period, and they presumably returned to normal lives.
Ed Moley was the president of United Broadcasting who impersonated the real Johnny Quick in a scheme to trump Quick's employer, Sees-All-Tells-All News, at getting news stories. This was reminiscent of United Broadcasting president Samual Tanner of Earth-One who, like his doppleganger Moley, sought to steal the limelight from his competitor Galaxy Communication's coverage of Superman, by having his chief scientist create the Blackrock superhero.
Charles Drake attempted to compete with Johnny Quick when both were given Quick's speed formula by the mentor Professor Gill. This mirrored the appearance of Don Allen, although unlike Drake, Don was of good temperament. Secretary Joannie Swift found a counterpart in Dawn Allen, having herself accidently gaining the secret speed formula and clad in a costume like that of Quick. Johnny was able to confuse her towards the end of her initial misadventure into forgetting the formula. Both the faux Quicks and Swift were only brief blips in the radar of super speedsters, but notable nonetheless.