Marvel and DC Comics are both notorious for how they screwed over the artists and writers who produced so many iconic comic book characters.
Marvel Comics went so far as to put a rights disclaimer on the back of the checks that it gave to its employees–cashing the check meant agreeing to forego all rights.
Below is a scan of a check from 1974 from Marvel Comics to artist Dick Ayers. The endorsement area of the check reads,
By endorsement of this check, I, the payee, acknowledge full payment for my employment by Magazine Management Co., and for my assignment to it of any copyright, trademark and any other rights in or related to the material, and including my assignment of any rights to renewal copyright.
