This section provides information on the variation of character interpretations both pre-Crisis and in iterations since Crisis. Focus is on characters defined by their given name (Alan Scott, Jay Garrick, etc.) rather than code name (Green Lantern, Flash). Emphasis is on interpretations where the character had a major role versus a cameo or non-essential story role to minimize clutter.
The Golden Age Atom
Prior Earth/Earth-0 = The Atom's history with the JSA was largely similar as Earth-2, minus whatever elements from Earth-2 that were missing on that earth. In this timeline, at the end of Crisis, the JSA was sent to Limbo to forestall the coming of Ragnarok and the Atom went as well (Last Days of the Justice Society #1). During the years in Limbo, Mary Pratt died, and the Atom emerged a widower. When the JSA returned to Earth in 1992 (Armageddon: Inferno #3-4), the Atom rejoined the Justice Society full-time (Justice Society of America #1-10, Justice League Europe #47-50). He also redesigned his costume to be more similar in appearance to the one he wore in the early days of his career (Justice Society of America #1). When Extant threatened the timeline during the crisis known as Zero Hour, the JSA led the battle against them. The Atom was the first of the original super-team slain in the battle, felled by a blast of chronal energy (Zero Hour #3). His body was later returned to Earth and laid to rest alongside fellow JSA members Hourman and Doctor Mid-Nite. It was also alleged that Al Pratt was the father of Grant Albert Emerson, later known as Damage, but the circumstances of this are controversial and likely confounded by a lack of credibility on the part of Vandal Savage, who claims responsibility for Damage's creation.
Revised Earth-2 =
Following the Flashpoint event, a separate Earth=2 emerged. In this version, Al
Pratt was a sergeant in the Army during the Apokolips War who survived an
atomic explosion, leaving him with super-strength and size changing
powers. He ultimate became an agent of the World Army and was killed
creating a haven for the survivors of Earth-2 as that world was
destroyed.
Earth-20 = The Al Pratt of Earth-20 is a college student disfigured by atomic radiation. His origins are unknown. (Multiversity: The Society of Super-Heroes #1).
Earth-21 = The Golden Atom of Earth-21 had by all accounts an essentially identical early history to his Earth-2 counterpart. Nothing is known of his later career after the dissolution of the JSA in 1951 (DC: The New Frontier LS).
Earth-22 = The history of the Atom of Earth-22 is largely similar to that of Earth-0. He was present at the battle with the Ultra-Humanite in 1950's but was defeated after turning against Dynaman upon realizing the villain's true identity. (The Golden Age LS). His later adventures are unrevealed, tho his godson Atom patterned his final uniform after the original Golden Age Atom appearance prior to his death in the apocalyptic battle at the Legion of Doom prison breakout (Kingdom Come LS)
