Fans of ABC's 'Castle' and Nathan Fillion alike know that the actor loves to indulge his 'Firefly' fanbase by including nods toward the legendary cancelled sci-fi series, everything from costumes to characters, but might season 5 see the biggest 'Firefly' reference to date?  Earlier we'd heard that a famous sci-fi director would helm an episode featuring a murder at a comic convention, but what about the murder is secretly a tremendous nod to Joss Whedon and Nathan Fillion's FOX past?

Browncoats unite, for 'Castle' season 5 will likely see the series' strongest 'Firefly' appreciation to date!  A few weeks back we learned legendary 'Star Trek: The Next Generation' star and director Jonathan Frakes was to helm an episode featuring a murder at a comic book convention, but the details of the murder are far more engaging.  Dubbed "The Final Frontier," the seventh episode of 'Castle' season 5 will incorporate a character named Gabriel Winter, known for playing "Captain Max Richards" of the brilliant-but-cancelled TV series 'Nebula 9!'

Sound familiar?  For those unfamiliar with the role that brought 'Castle' star Nathan Fillion to stardom, the actor portrayed "Captain Mal Reynolds" of the brilliant-but-cancelled TV series 'Firefly.'  Coincidence?  We think not.  But where Fillion has maintained a lucrative post-'Firefly' career, "The Final Frontier"s Gabriel Winter seems to have descended into alcoholism and one-night stands.

Elsewhere, we know that ‘30 Rock‘ star Kevin Brown will put in an appearance for a ‘Storage Wars’ -type episode, and that former ‘Heroes’ and ‘The Office‘ star Jack Coleman will guest as a recurring senatorial antagonist for Beckett.  Coleman’s character may or may not have ties to the man who attempted to kill her, Cole Maddox (‘Battlestar Galactica’s’ Tahmoh Penikett).  Of course, ‘Castle’ season 5 will also deal with the fallout from its two leads finally hooking up in the season 4 finale!

What say you?  Will 'Castle' season 5 episode "The Final Frontier" prove the series' most meta yet?  How long before Nathan Fillion gives up all together and re-lights the 'Firefly?'  Give us your predictions for 'Castle' season 5 in the comments!

(Via E!)

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