Fans are itching for Nathan Fillion to star in a live-action Marvel movie. In the past, he's worked with Joss Whedon (Firefly, Dr. Horrible's Sing-Along Blog) and James Gunn (Slither, Super), who are both on the studio's payroll. Gunn is slated to direct Guardians of the Galaxy, so we're all wondering whether Fillion's on his cast list.