The Legal Contract on the Back of a Paycheck Link
According to this BoingBoing story Disney/Marvel are asserting their ownership of the Ghost Rider character.
"In response, Marvel argued that it was Friedrich who had relinquished all rights to his creations by signing his checks—all of which came stamped with legalese spelling out that his was a work-for-hire contract only..." Just think about that for a second. The back of your paycheck could be an additional contract above and beyond the contract for employment.