Adam Baldwin Previews His Castle Visit (Firefly Shout-Outs Included), Reflects on Chuck Finale

Rick Castle is about to get Slaughtered.

In this Monday’s episode of Castle (ABC, 10/9c), Nathan Fillion’s novelist will dive head first – for better or for worse – into a storyline with a rough, tough and gruff NYPD detective named Ethan Slaughter and played by Adam Baldwin.

And while the episode obviously offers the geeky thrill of a reunion between the onetime stars of Firefly (where Fillion played Capt. Mal Reynolds to Baldwin’s Jayne Cobb), it will also serve a larger purpose, as the ABC hit closes in on its “very emotional” Season 4 finale (airing May 7).

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Still processing the discovery that Kate remembers her shooting and the aftermath, “Castle is trying to figure out how he feels about Beckett,” series creator Andrew W. Marlowe tells TVLine. “He feels likes he’s a bit uninspired by her because of all this stuff that’s going on, but he hasn’t articulated that yet. So when he sees this larger-than-life cop figure on the news, he thinks, ‘Maybe I just need a new muse?’”

And make no mistake, Slaughter as a decidedly different muse will amuse. “He takes Castle on quite the ride,” says Marlowe. “Maybe it’s the most exciting case of his life, or maybe it’s, ‘The grass is always greener.’ That’s the journey he goes on.”

Baldwin tells us that Slaughter’s first assessment of Castle, when the author seeks to shadow him, is, “He’s a bit not up-to-snuff. He’s a bit soft. But he likes him, so he’s going to give him a shot.” And hopefully in doing so put some calluses on this writer’s hands. “He wants to mold him into a better law-fighting man.”

And does Castle indeed emerge from the experience a changed man? “He gets to be in the line of fire,” Baldwin previews. “And that’ll change anybody, getting shot at!”

Baldwin also echoes that which Fillion teased at PaleyFest, that in dipping his toe into Slaughter’s wilder world, “Parts of [Rick's] face will be rearranged.” After chuckling some, Baldwin affirmed, “Yeah, you can expect to see him get a little roughed up.”

But along the way, Baldwin stresses, he and Fillion were sure to weave in some comedic moments between two old friends. “To have that natural chemistry that we had from eight years ago, to look at Nathan’s face and ‘get’ exactly what he’s thinking, was great,” he says.

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The reunion was also certainly overdue. “Fans have been prodding us to share some scenes,” Baldwin says, be it on Castle or the since-expired Chuck. (During his run on the NBC spy comedy, Baldwin only enjoyed Firefly alum Summer Glau as a guest star.) “Anytime I get to work with anyone from that universe is a ‘resurrection,’ if you will,” he enthuses.

To date, Castle has planted scarce Easter eggs for Fillion’s Firefly faithful, including cameos by a “catalyzer” as well as Mal’s brown coat itself. In this week’s episode, Baldwin says to keep an eye and/or ear open for “subtle” nods to the sci-fi series, “but nothing overt.” (As Marlowe himself explains, “Just having Adam and Nathan on screen together is a lot!”

Turning from Firefly-class spaceships to relationships, can Castle viewers expect Slaughter to sense that his new “partner” has feelings for Beckett? And if so, does he offer any guidance? Says Baldwin with a chuckle, “He will definitely have a few words of advice, in his own colorful way.”

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Before bidding Baldwin adieu – and on the topic of TV romances – I asked if he believed that Chuck‘s John Casey was now enjoying some badass version of “happily ever after” with Gertrude Verbanski (played by The Matrix‘s Carrie-Ann Moss), as teed up in the series finale. “Oh, you bet,” he theorized. Because although Baldwin had lobbied toward the end for Casey to “go out in a blaze of glory” and die a hero’s death (“I couldn’t sell them on that,” he half-grumbles), “I liked that Casey ended up going to be with Verbanski, because she is hot.”

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