Nathan Fillion's Firefly Homage On Castle Was Absolutely Perfect

Nathan Fillion has racked up a few long-running shows in his career, like "The Rookie" and "Castle." Fillion is among many who are still heartbroken that "Firefly" only got one season in 2002 before its cancellation. Although an animated "Firefly" series is in development, "Castle" was the last time Fillion got to step back into Mal Reynolds' shoes.

The ABC procedural series saw Fillion play Richard Castle, a crime novelist who partners with the NYPD to help inspire his next novels, only to fall for detective Kate Beckett (Stana Katic). In Season 2, Episode 6, Castle tries on his nondescript "space cowboy" outfit for Halloween, and it's the Mal Reynolds costume from "Firefly."

Castle's daughter, Alexis (Molly Quinn), points out that it's a little old, saying: "Didn't you wear that like five years ago?" She then asks him if he should "move on" from it, while western music plays in the background. It's a tongue-in-cheek interaction about how the love for "Firefly" and the calls for its return have never really died down, even after the 2005 revival movie "Serenity."

Mal Reynolds' costume is the most obvious "Firefly" homage in "Castle." It's unsurprising that Nathan Fillion would tie the shows together, as it's well-known that "Firefly" and "Castle" are two of Fillion's best TV shows. Meanwhile, there are also other references to the genre-defining sci-fi series, according to Fillion.

"That whole Halloween episode where I dressed as Mal Reynolds — the audience loves that. They know it's a TV show. So to see those little nudges and winks, it's great," he told Spoiler-Alert. "The first time Castle put on gloves at a crime scene, they were blue: like 'two two, hands of blue.'" That's a reference to a pair of mysterious assassins in "Firefly" who wore blue gloves to assassinate people for the Union of Allied Planets.

Fillion also added: "I didn't ask, I just did it, and people live for that stuff. In the Halloween episode, I hid a prop from 'Firefly' on the set." The prop in question is the ship's glowing compression coil and it can be seen on the shelf in Richard Castle's apartment.