Also, Joss Whedon said somewhere that he was done with "Firefly" unless he could get all the actors together again. While I don't necessarily agree you need all nine (and two of them written out by the movie), I can't see a show with just Mal, Zoe, Kaylee & Simon being all that good. Jayne, Inara & River all have other TV shows, with apparently bigger parts than 1/9th of a lead. Morena Baccarin is one of the top-billed stars of her show, Summer Glau has a new show coming out and why would Adam Baldwin leave a job that has proved a lot more steady than anyone expected to retry something that already failed? Of course, you could say the same thing about Fillion and "Castle," but IMO, his new show is a waste of his talents. "Castle" is basically one facet of Reynolds' personality. The goofiness and sometimes spastic or whacky antics of Reynolds are what people remember, but they worked so well on "Firefly" because they balanced out a character who was a seriously bad dude who was decisive & violent when called for, and had a dangerous physical presence. Playing a dorky goofball who only comes through with the action in extraordinary circumstances is a waste of a large part of Fillion's range, and gets tiresome on its own after a while, which is why I periodically fall out of interest with "Castle". The supposed chemistry and sexual tension with his co-star is somewhat undercut by her being basically a girlier version of Zoe, whom "Firefly" firmly established as having zero sexual chemistry with Mal. And the action gets harder and harder to believe when the skinny chick (no matter how many overcoats she wears) always has to save the big guy whose appearance is described more than once on the show itself as "rugged." Whenever Beckett talks down to him regarding a danger scene, I can't help but think that Zoe would use her as a toothpick, and she called that same man "sir." On the other hand, eye-candy aside, the best thing about Chuck is seeing Casey working "undercover" at Best Buy. Despite his lesser role to another skinny chick who should not be able to kick half the asses she does, and a less funny & more dorky (than Castle) nerd, the role of Casey seems to have more gravitas and significance, at least because an "attaboy" from him is worth something. Sarah's got all those chick-feelings and hormones and whatnot compromising her Chuck-judgment, and the rest of the characters are even bigger losers or forced to like Chuck because he's family. When Casey approves of him, or sticks up for him - THAT is an affirmation of the man-child's progress.

What I'm getting at is, from a Firefly perspective, you can see why Fillion might be more than willing to trade metrosexual hic for his brown coat again, but the other half of the two best characters on the show might be in just the opposite position. And if Summer Glau's new show takes off, Joss Whedon is going to be in a fix if he can't invent sci-fi excuses for a skinny chick to kick ass.