The Doom Patrol and the Fantastic Four
This is not exactly the most pressing problem facing the human race at the moment, but it's something that occurred to me years ago and I wonder if fans have discussed this at all. DC's Doom Patrol and Marvel's X-Men debuted close enough that many commentators think there was some shenanigans involved, either coincidental similarity or outright theft of ideas. Both teams have a leader stuck in a wheelchair, the members are regarded by the public as freaks and outcasts, so on. But when I read Henry Kuttner's "Baldie" stories about an ongoing secret war between two groups of telepathic bald mutants (!), I figured 'well, heck. Long-time pulp readers Lee and Kirby got the idea for the X-Men from Kuttner.'
And I also had the feeling the Doom Patrol was DC's effort to copy the Fantastic Four, not the new X-Men. The Patrol members fought and argued with each other as Marvel characters did, but in a way rare among DC's more civil heroes. Negative Man can be seen as a clear imitation of Human Torch... color him red with a yellow aura and see what I mean. Robotman is not blue or gray like most metal characters but more that brownish-yellow that the Thing was before he went brighter orange. Both are the strongmen of their teams, both rough-mannered and both running amok at a few points.
Reed Richards became the Chief, still a brilliant scientist but now paralyzed from the waist down... and some of his stretching ability was given to the female member of the team, Elasti-Girl (oooh, that name is a giveaway!). Although she nominally had the power to shrink or grow, she frequently enlarged just arm, stretching it to swat a bad guy. Sue's invisibility power was discarded.
When Beast Boy was added, the resemblance is even stronger. He's an insolent wisecracking teenager who feuds with the tough strongman of the team in the Torch-Thing manner.
Research continues! I'll need a couple hundred dollars to hit the comics shoppe for back issues, let me see what I can scrounge up.
[Aw. Never mind. A quick hit on Wikipedia shows this idea is not exactly a stunning revelation never thought of before. Still, I suppose it's worth mentioning.)