Nathan Fillion

LOS ANGELES - Nathan Fillion has played many roles on television over the last decade, and recently appeared as the crooning villain in the Internet sensation "Dr. Horrible’s Sing-Along Blog." But he was last seen in prime time bloodied and bruised departing Wisteria Lane, one of many men with the misfortune to have been attached to one of the "Desperate Housewives." When he returns to ABC on Monday at 10 p.m., he will be the one kicking butt as the title character in the new dramedy "Castle."

A police procedural with a lighter touch, the series chronicles the best-selling mystery author Richard Castle. The writer tags along to crime scenes looking for fresh inspiration to the dismay of NYPD detective Kate Beckett (Stana Katic).

Addressing reporters here recently, Fillion said it was easy to say yes to the series since it offered a chance to flex a few more of the acting muscles than required on "Housewives."

"I spent a lot of time sitting around in a living room saying ’Uh-huh. Yes. That’s right. Well, I’ll back you up on that,’ " said Fillion.

By contrast, the mischievous and cocky Richard Castle knows how to have fun. "Every day of his life is a field trip," Fillion said.

The actor began boning up on mystery novelists after taking the role and has taken to Boston author Robert B. Parker’s "Spenser" series in particular. "Something that [he’s] done very, very well is his attention to detail. That’s also, I think, one of Castle’s strengths. He pays very, very close attention."

Castle is more than that, the actor admitted: "He is a spoiled brat. He’s in his own world, but he’s a clever guy."

As the swashbuckling but cranky space captain in the short-lived cult series "Firefly" - and its big-screen spinoff "Serenity" - Fillion has built a solid following among sci-fi fans over the years. Those projects were helmed by fellow sci-fi favorite Joss Whedon, as was "Dr. Horrible," and Fillion believes those fans will appreciate the earthbound "Castle."

But even if they don’t, they probably won’t let him know. "They’re always very polite. They’re kind of Canadian in that way," quipped the Edmonton-born actor.

When asked if he is the next Angela Lansbury, of "Murder, She Wrote" fame, Fillion didn’t miss a beat. "That’s what I like to say: If Angela Lansbury was more manly - but just a little."