The Fastest Man Alive. On at least three of the parallel planets in adjacent universes, three men were labeled by this term: Barry Allen, Jay Garrick and the man who would be Johnny Quick. However, as revealed upon reviewing data obtained from the Multiverse, the heroine Donna Troy aka Wonder Girl learned of the existence of a Flash on each Earth.
Some more famous than others, some noble while others infamous, each with different strengths and weaknesses both in ability as well as character. Nevertheless, every incarnation of the Flash was a necessary component in the fabric of his own distinct dimension's diorama.
On Earth-One, Barry Allen was charged with superspeed force when a bolt of lightning shattered chemicals that splashed upon him, becoming the Flash.On Earth-Two, Jay Garrick had succumbed to the powerfully potent fumes of hard water which mutated his body to react as superspeed as the Flash.
On Earth-Three, a malcontent criminal obtained a powerful helmet that while wearing it provided him superfast powers as the evil Johnny Quick.
On Earth-S, Kit Freeman as Kid Eternity accessed his world's speed force...Eternity... allowing him to call upon heroic Mercury and Thjalfi often.
On Earth-D, Tanaka Rei gained superhuman speed through undisclosed means whereby he adopted an alias of that of his comicbook idol the Flash.
On Earth-X, an individual under the employee of Nazi Germany was provided abilities comparable to the speedsters then quickly disappeared.
On Earth-Four, the Crisis on Infinite Earths prevented the appearance of its own potential fleet fighter who would've debuted at some point thereafter.
On Earth-Six, on a world that had as its premier protectors as their Monarchy it was only natural that their scarlet speedster himself would be a knight.
On Earth-Twelve, Mister Cramer attained the flying and superspeed abilities of the Freedom Brigade's Captain Swift, father of Inferior Five's Blimp.
During a Crisis on three worlds, Kid Etnerity called upon Mercury to assemble heroes from his Earth-S as well as Earths One and Two. Among these were Barry Allen and Jay Garrick, who as the Flash sped alongside Kid's swift alter ego. And it would be Mercury who founded the second incarnation of the Squadron of Justice, mirroring the Justice League and Justice Society.