Castle

Ten years ago — (or was it 500 years from now?), Nathan Fillion and Adam Baldwin were trapped together in space on Fox's short-lived, but much-beloved sci-fi adventure series, Firefly. Though Nathan's Captain Mal Reynolds often clashed with Adam's Jayne Cobb, the actors developed a strong bond that survived post-cancellation. The two buds reunite on the April 16 episode of Castle (titled "Headhunters"), but don't expect a recreation of their Firefly characters' relationship. "It's flipped," explains Adam. "Nathan's the dumb one this time."

"Yup," echoes Nathan. "Adam's in control, pulling the strings and I'm tagging along in the dark."

The episode finds Castle abandoning Beckett to shadow Adam's tough gang squad cop, Ethan Slaughter. Between takes, the two had the chance to reflect on their favorite Firefly moments. Nathan says his is "the one where Adam's in the airlock. It was the scene that let everybody know Jayne, this big lovable character, was not to be trusted and would sell you out if he got the chance."

When Firefly ended, both actors swiped some treasured memorabilia from set. "I kept Jayne's boots, knife, knitted hat, T-shirts and a model of his head," says Adam. "But I auctioned off a lot of that for charity."

Nathan's collection includes three of Malcolm's guns: "One fake foam one for stunts, one wood-filled resin one for practice and one actual gun," says the star, who also owns two of Mal's holsters.

While neither actor seems particularly hopeful that they'll ever get to use these props again on camera in another Firefly project, there could be more Firefly reunions on Castle if Nathan has his way. "I've been pitching an episode where the lead actor of a failed TV sci-fi series gets killed, and it turns out the whole cast and writers hated him and are all suspects," says Nathan. "It would be very exciting for Firefly fans because I'd want to get everybody back for this episode, but with Adam on this show, he's single-handedly ruined that! But I can still have my hope."

For more on the actors' Castle reunion, pick up the April 16 issue of TV Guide Magazine!

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