First Appearance: USA Comics #1 (August 1941).
Golden Age Appearances: USA Comics #1-2, 4, 6, 8-12, 14-17, All-Winners Comics #2-5, 7-11, 19, 21.
Modern Appearances: Giant-Size Avengers #1, Marvel Premiere #29-30, Invaders #6 & #35-41, Invaders v2 #1-4, Fantastic Four #150, 405, Avengers #151, 153-156, 160, 164-165, 172-173, 185-186, Avengers Annual #6, Vision and the Scarlet Witch v1 #1-2, Marvel Two-in-One Annual #1, Marvel Universe #1-3, Super-Villain Team-Up #9, Contest of Champions #1-3, Thor Corps #2, She-Hulk v2 #22, Citizen V & the V-Battalion v1 #2, v2 #1.
Years Active: 1941-present.

Dr. Emil Frank is deep in the African jungles when his son, Bob, comes down with a fever. As he lays dying, a snake moves to bite Bob, only to be killed by a mongoose. Dr. Frank is seized by the idea of giving his son a blood transfusion from the mongoose.

No, really. See, Emil's reasoning is that since the mongoose can kill the snake, maybe the mongoose's blood can kill the snake's venom. It makes a certain amount of sense, if you can grok the Golden Age logic of it all.

The transfusion works, curing Bob Frank and giving him superspeed.

No, really. See, since the mongoose is very quick, wouldn't the mongoose's blood lend a transfusion recipient that same speed? It makes a certain amount of sense, if you can grok...well, okay. It doesn't make any sense, and is in fact perhaps the silliest origin of all time. But it was the Golden Age, and standards for origin stories were different back then. (Ronald Byrd points out that one GA story had the Whizzer's power come from a secret written in a journal handed down from Egypt.)

Anyhow. Dr. Frank dies of the strain caused by the excitement. So Bob Frank goes to New York, puts on a yellow and blue costume, and goes out to fight crime and the Axis, eventually joining the All-Winners Squad. During his adventures in the Golden Age he is shown, on more than one occasion, to be active in African-American neighborhoods--a rarity for GA heroes--and to have an African-American sidekick named "Slow-Motion Jones."

When the Whizzer was brought back, in 1974, more of his past, including what happened to him after the war, was revealed. He joined the Liberty Legion and met and fell in love with the heroine Miss America. After the war ended both Miss America and the Whizzer joined the All-Winners Squad and were active with the team until it disbanded in 1949, at which point they married. The pair went to work for the U.S. government, doing security and other odd jobs. In 1960, while they were guarding a secret nuclear project, they were exposed to radiation due to sabotage by an old enemy of theirs. Miss America was pregnant at the time, and when she eventually gave birth, the child was an irradiated mutant. The child was taken into custody by the government and eventually grew up to be Nuklo.

The Whizzer and Miss America left the facility on a pension and began touring the world. Miss America became pregnant, and the pair went to Wundagore Mountain for her to give birth, but the baby was stillborn, and Miss America died of radiation poisoning soon thereafter. Crazed with grief, the Whizzer fled and for the next few decades (originally only two decades, but that is no longer viable) wandered the world as a mostly-amnesiac vagabond. He eventually read about the exploits of the Scarlet Witch and Quicksilver and came to think that the pair were his children. Some time later the Whizzer came out of hiding and had a few adventures with the Avengers, trying to gain custody of Nuklo and associating with the Vision and the Scarlet Witch. The Whizzer eventually died in battle, although his actions helped cure Nuklo.

Citizen V & the V-Battalion #2 reveals that the Whizzer, with Miss America, was a founding member of the V-Battalion's Penance Council. In 1953 he attended the funeral of Union Jack (II).

Note: In at least two stories it is claimed that the Whizzer's real name is "Jack Robinson," as in, "Quick as Jack Robinson." We'll just have to assume that that was a cover identity.