Castle is an American comedy-drama television series that premiered as a mid-season replacement show on March 9, 2009 on the ABC Network. The series is about Richard Castle (Nathan Fillian) who, as a famous mystery novelist is asked by the New York police department to help solve a set of copycat murders that appeared to be based on some of the scenes within his bestselling novels.
When Castle is thrust on detective Kate Beckett (Stana Katic) she is reluctant to use him partly because of his notoriety as a writer, and partially because he is a civilian who is not trained as a law enforcement officer. When he steps in, their personalities instantly clash but by the end of the initial show, things mellow out and other types of sparks try to ignite.
Prior to this first investigation, Castle had a string of books on the best seller list. In his last book he had killed off his main character. He had become bored with his success. His ex-wife/publisher was hounding him to come up with a new character. After his work with the NYPD, he found his inspiration: Beckett.
Because of his fame and fortune, Castle pulled in connections with the Mayor who convince the police commissioner to assign him to Beckett's division so that he could continue his research. Much to Beckett's chagrin she is now the model for the new Castle creation, "Nikki Heat."
What makes Castle such a likeable show is its quirkiness, irreverence, and phenomenal cast of characters. As with shows like Numb3rs and The Mentalist, Castle has a main character that is out of his natural element and therefore provides a view through a different set of glasses. The show is irreverent in that it does not take itself too seriously and is willing to have Castle walking around in police gear that says "Writer" on the jacket instead of "Police."