In a move that reportedly caught Wall Street off guard, Avi Arad, whom many analysts have called the real superhero of Marvel Entertainment, resigned Wednesday as chairman and CEO of the company's film studio and chief creative officer of the parent company. He will now head his own company, Avi Arad Productions, which will continue to produce films featuring Marvel's superhero characters, including next year's Spider-Man 3. The move comes just days after X-Men: The Last Stand set a Memorial Day record at the box office and on the same day that Arad sold 3.15 million shares in Marvel Entertainment, worth $60 million, that vested last Friday. According to trade reports, some analysts speculated that Arad was leaving the company because he disagreed with its decision to fund several upcoming films on its own through a $525-million debt facility set up by Merrill Lynch. "This is not a ringing endorsement of company strategy," Banc of America analyst Michael Savner told Daily Variety. "He may understand something about the company the street doesn't," said Evan S. Wilson of Pacific Crest Securities in an interview with the New York Post. Marvel's shares tumbled by more than 5 percent on the news Wednesday.