Believe it or not, I do believe that they're actually rip off of The Heap character found in the Airboy comics.
The Heap is a public domain character that have no copyrights, so they can't sue each on that because it must have been based off the Heap without knowing that each other is doing the same thing.
The co-creator Swamp Thing writer, said that when he found out about the Man-Thing that came as a surprise while he was working on Swamp Thing with the artist. He decided to give Man-Thing the burning touch to make it different from the Swamp Thing otherwise they're more of same.
I shouldn't be surprised that he's being used more now thanks to the internet that give information and knowlegde on the public domian comic books, because he's been in public domain for years and will never be pulled out after that.
I did ask myself that should I use this Heap in my future comic art? I would said no, because the Heap looks ugly as hell and I rather be working on the Man Thing or Swamp Thing who looks much better anyway. Bernie Wrightson is outstanding as a co creator, he makes Swamp Thing looks more awesome than any artist who did swamp thing. Same thing with Steve on the Alan Moore's Swamp Thing run. Man Thing is also great looking drawn by Frank Brunner and others.
One of my favorite artists, Tom Sutton's artwork on the heap shows that it's still difficult to make him look more interesting and fresh. But really, he's more like a tar monster to me found in a Scooby Doo cartoon.
The Heap is a old design that feels lame and weak by today's standard looking like a walking green glass guy. However, it's still a important part of the history behind the creation of the Swamp Thing and Man-Thing. I feel that the Heap do still have interesting future stories left in him to be told by many new writers and drawn by horror artist who would make it look more interesting than it is right now.
woah slow down, deadpool may be coolrer than deathstroke but he could never be better than deathstroke. deathstroke beat green arrow, zatanna, the atom, hawkman and the flash at the same time. he will ALWAYS have props for that.