First Appearance: Marvel Boy #1 (December 1950).
Appearances: Marvel Boy #1-2, Fantastic Four #164-165, What If v1 #9, 4 #1.
Years Active: 1950 to the present.
In 1934 Professor Matthew Grayson, sick of the tyranny of Earth's governments, built an experimental, uranium-powered rocketship which he used to transport himself and his infant son Bob to Uranus. Once there the pair discovered an advanced civilization, manned by Uranian Eternals. As Bob grew up, he developed telepathy and an advanced intellect, as well as superhuman strength. In 1950, at the age of 16, Bob returned to Earth at the suggestion of his father, who told him that Earth needed his superhuman abilities. Bob was given pills, which would enhance his strength, and a pair of wristbands, one of which could project light. On Earth and Uranus, Bob used his abilities and flashy costume (with embarassingly short shorts) to fight crime as Marvel Boy (III).
In the modern era it was revealed that after various solo adventures Marvel Boy (III) was contacted by FBI agent Jimmy Woo and recruited to fight alongside Gorilla-Man, the Human Robot, Venus, and 3-D Man as the Avengers against the Yellow Claw.
More recently still was the mini-series Avengers Forever, in which this adventure was erased. In current Marvel continuity Marvel Boy (III) and the rest of those individuals were still active in the 1950s (see the Human Robot entry for why this is probably not such a great thing), but they never formed together as a team.
In the late 1950s Marvel Boy (III) received a message from his father requesting medical assistance. Marvel Boy (III) returned to Uranus without the needed supplies, only to find the colony of Uranians destroyed; they had grown weary of life and so a cosmic death-bringer obliged them. In an insane rage, Marvel Boy (III) returned to Earth to punish a bank manager who had refused him a loan for the medical supplies; on the way back to Earth his ship was exposed to an unknown form of radiation which placed him in suspended animation, and it was only decades later, in the modern day, that he arrived back on Earth. When he finally did arrive, he went on a rampage, and ended up dying in combat against the Fantastic Four.