Parody is really a defense in a  case of copyright infringement.  The issue is whether or not the use is "fair use" of the alleged infringed copyright or trademark.  Unfortunately, there is no easy yes or no answer in this case.  Courts deal with the matters on a case by case basis looking at various factors including the actual product or art work themselves.  So I would say that you should err on the side of caution and take what you have developed to an attorney that deals with copyright and trademark law and discuss the issue with him or her.  Bring your cartoons.  It is better than starting to sell them and then having a cease and desist letter come in the mail.  May the force be with you.