Mongoose blood? Heavy water, sure, but mongoose blood?

Flash (Jay Garrick) - Whizzer (Bob Frank)

Here be the second post that finds Golden Age characters with similar abilities paired with one another, which hopefully compensates for a lack of same in pairings of silver-, bronze- and beyond- characters…

So here we have the very first speedster, the template for every character conceived similarly since. Including the second cited here, whose origin is universally mocked as the most poorly-aged provenance of the Golden Age: he gained his super-speed due to a transfusion of mongoose blood.

Commonalities:
The original speedsters of their respective diasporas.

Differences:
None to speak of, other than one is a key character in the history of superhero fiction, and the other is regarded fondly for the reason cited above.

Alternate histories:

FL: A young man named Jay Garrick is gravely injured in 1940; he receives a blood transfusion that activates a meta-human gene which grants him the ability to move and react at superhuman speeds. Taking the codename the Flash, Frank combats crime and the Third Reich throughout the 1940s and joins the Justice Society. He marries another extra-normal operative, but their union is doomed when the two are exposed to radiation. Years after the woman dies, the Flash reappears and briefly works with the Justice League before he dies himself.

WH: A young college student named Bob Frank inhales experimental “heavy water” fumes, which activate a mutant gene granting him the ability to move and react at superhuman speeds. He takes the codename the Whizzer and combats criminals and the Third Reich and co-founds the Liberty Legion. The Whizzer retires for several decades, but in recent years has returned alongside other Legionnaires: due to his retarded aging, he is active mentoring novice superhuman operatives.