What makes this more than just the average creator rights lawsuit is Marc Toberoff is heading it. Toberoff is an intellectual rights lawyer. He's the lawyer that won the rights for the Siegel heirs. Similar to the Siegel case, the Kirby Estate is looking to regain their share of copyright over the characters in comics and other media. According to Rich Johnston:
This isn't the first time Kirby and Marvel has battled over creator rights. The Comics Journal reported how Kirby fought against Marvel for years over the ownership of his original artwork. Marvel had insisted that Kirby sign away the rights to the characters and if he didn't they would retain all of his original art. It was in 1978 when copyright laws changed that publishers had to make sure all their paperwork was in order when dealing with work for hire relationships.Such claims, if found valid, would begin from 2014 and, as always, its worth noting that Marvel/Disney will still own the trademarks of the characters in comics, and the studios in movies. The likelihood is that, if successful, the Kirby estate would enter into negotiation with Marvel over terms to continue publishing comics based on his work.
When DC started moving towards acknowledging the rights of creators between 1973 and 1978, Marvel decided to follow similar practices by returning art and paying royalties (which they referred to as 'incentives'). DC had begun to return its backstock of original art to its owners but Marvel held on to some. There was no clear indication why certain artists only received a portion of their artwork. There was a question as to how Marvel was cataloging the art and whether or not some had simply been lost or stolen.
In 1984, Marvel finally started returning the art, Kirby only received 88 pages out of more that 8000 he had done. When Marvel returned the art, the artists had to sign a release statement saying the art was a 'gift' from Marvel. This also stated that the creators agreed the art had been 'work for hire' and Marvel still was the "exclusive worldwide owner of all copyright" related to the art. Kirby had not been given this option. He alone was given a different form to sign that basically said he was able to store the artwork on Marvel's behalf. Should they require the use of the artwork, Kirby was to return it given a proper amount of time. In other words, all Kirby could do was hold onto the art, nothing else. Kirby wasn't even allowed to sell his own artwork.
The characters involved include the X-Men, The Avengers, Iron Man, Hulk, Captain America, Thor, the Fantastic Four among others. Given that the Marvel/Kirby relationship hasn't been the best, it's no surprise that this case has arisen. Who is in the right? Marvel holds the rights but should the heirs get a piece of the action. Without the contributions of the creators, publishers like Marvel and DC wouldn't be where they are today. Part of the question could be how much of the success is from the actual creation versus how much has been from marketing and continued use?