I didn't realize before that Pep Comics featuring The Shield came out well over a year before Captain America. The character origins are somewhat similiar. Both received their powers from a chemical serum by a chemist that would later be killed by Nazi's. Captain America's original heater shield was also too similiar to the shield that the Shield wore as part of his costume to be a coincidence. I had never really paid much attention to the Shield character but I had always figured it was their attempt to rip off Captain America until I noticed recently when the first Pep Comics was released.

Wow, never knew that. But then, comics have a rich history of borrowing ideas from each other, so one should never assume anything in comics is original.

Same with the Doom Patrol and X-Men. They were released only months apart with Doom Patrol coming out first. Obviously, different powers but the same premise.

Outside of their mentor/leader being a professor there is just enough differences where they are not a carbon copy.
a. The X-Men where born with a mutated chromosome that gave them their powers.
b. The X-Men were teenagers.

Yes, it has been pretty common knowledge that Marvel "borrowed" the idea from the Shield character in Pep Comics. Even Cap's shield was triangular, similar to the Shield's costume. How they got away with this, I don't know.

Professor X idea also came from a character named Tad Carter that Stan Lee and Ditko created in Amazing Fantasy #14. This character has very similar powers as Charles Xavier but then Carter was introduced as part of the 616 Universe in the X-Men Hidden Years book.

I read at another forum that they changed Cap's shield because of complaints from a rival company, Archie Comics I'm presuming. There were no cites though.

Yeah but really I always saw Doom Patrol as a copy in many ways of Fantastic 4.

Guy in a body he doesn't like that is strong and powerful Thing/Robot man

Super genius Reed/ The Chief

Energy based power who flyers and blasts Torch/ Negative Man

Super stretchy Mr Fantastic /Elastic girl

Create invisible force fields Miss Invisible /mento

I mean thats a lot closer than the correlation between DP and X-men

Fantastic Four being a copy of Challengers of the Unknown (well, Kirby redoing his own stuff I guess)...

The theory has long been that there's no way the Doom Patrol and X-men were intended copies of each other unless the writers/artists were talking to each other directly, given how closely they came out.

I could have sworn I read that there was some kind of artist or writer connection between the two books but I cannot recall what.

The co-creators of Man-Thing and Swamp Thing were roommates around the time they were created. Maybe that's what you're thinking of.

Actually, that indeed might be what was thinking of. And they both were inspired by The Heap.

Marvel didn't totally get away with it as they had to change Cap's shield to a circular one. But Simon and Kirby decided to have him throw his shield which only enhanced his popularity so that backfired against MLJ. Ironically the original started to copy the more popular imitation. The Shield gets his sidekick Dusty and his powers got greatly diminished (although an occasional flare up of his old strength popped up till it faded completely)! I was half surprised that Republic did Captain America who they made unrecognizable in the movie serial instead of the depowered Shield that they could well have adapted faithfully. But I guess Captain America was so much more popular they went with the bigger name! Over the years there have been a number of different versions of the Shield and I rather liked all of them. Also I liked The Fly (not counting the Campy Fly-Man years) among their characters. A lot of their 1960s heroes were not great (Mighty Comics Group anyone?) but the 1940's versions of them were surprisingly good! Liked the 1980's revival for awhile too till they started to make a lot of bad decisions (getting rid of the very different 1950's Shield who like the Fly was a Simon and Kirby creation in favor of Steel Sterling? Madness!). More recent attempts keep failing too which is a shame. Archie Comics could have been a contender!

The 1940s Heap not to be confused with the 1970s Heap of Skywald fame!

Arnold Drake went from writing the one company's book to the others, I think that he wrote Doom Patrol and years later wrote the X-Men!

Also Elasti Girl could increase her size as well like Marvel's Gi-antman! One unforgettable cover had her squaring off against a giant robot (you could see in a transparent part of the robot's head the guy at it's controls!) swinging a submarine at her like a baseball bat!

Several not-especially-knowledgable-sources seem to think there's something to it, but given that it seems to go Challengers --> F4 --> Doom Patrol --> X-Men, it's a LOT messier than that.