Join the star of ABC’s TV series "Castle" actor Nathan Fillion ("Firefly," "Dr. Horrible’s Sing-Along Blog") as he discusses the new season of his show. "Castle" is a witty drama based on a famous crime and horror novelist, Richard Castle, who helps the NYPD homicide department solve crimes. The second season began September 21st at 10 pm ET on ABC, and is available as of September 22nd on iTunes for download.