It's been 23 years since Fox summarily canceled Joss Whedon's single-season science fiction show Fireflybefore even airing all its episodes, and 21 years since the spin-off movie Serenity brought the cast back together for what seemed like a final story. The series earned a passionate fan base during its short run, and was popular enough to spark a series of spin-off novels, comics, and graphic novels. Since then, there have been convention cast reunions and periodic rumors of a possible series revival, but nothing more concrete. For the past week, though, Firefly star Nathan Fillion has been teasing something new for the Firefly crew.