http://www.imdb.com/title/tt0112175/trivia
A sixth season was planned for "Spider-Man" which would have had Spider-Man find the real Mary Jane Watson from limbo with the help of Madame Web. Story editor John Semper said in an online interview that it purposefully left unresolved to see Spider-Man find the real Mary Jane because the crew thought they were going to get another season or two of "Spider-Man". However, Margaret Loesch, who was the president of Fox Kids network at that time, hated one of the show's executive producers, Avi Arad, and she wanted to put Arad out of business. When the sixty-five episode contract for "Spider-Man" was up, Loesch decided to cancel the show and had permanently shut down Marvel Films Animation, the company that provided the animation for Spider-Man.