Richard Castle, successful murder mystery novelist, is played by actor Nathan Fillion.
When he became an author, he changed his name from Richard Alexander Rodgers to Richard Edgar Castle. Edgar is in reference to Edgar Allan Poe.
Castle has been married twice. He has a fling with his first ex-wife Meredith, a wannabe actress and mother to Castle's daughter Alexis, but refers to her as a "Deep Fried Twinkie" (guilty pleasure that you can only have once in a while). Their marriage ended because she cheated on Castle with a colleague of hers and because Meredith felt she didn't know Castle as well as he knew her. He refers to his first marriage as "Betrayal, Lies, Deceit."
Castle's second ex-wife, also his publisher, is Gina Cowell. Regarding why their marriage failed, Castle calls her "high-maintenance" and a "shopaholic"  where Gina says he was so overprotective of Alexis that she felt like an outsider. They get back together after Beckett rejects his invitation to join him and Alexis at his house in The Hamptons for the summer because she is in a relationship with Detective Tom Demming. When he returns to the precinct in the fall, they are still together. However, they have a loud and public argument (described by Martha as a PDA: public display of anger), which appears as a story in a gossip newspaper and thus becomes a topic of conversation around the precinct. Gina calls Castle's phone numerous times to talk things over, but he refuses to answer. Martha finally talks the problem out of him: they aren't in love anymore and Castle wants a more magical relationship. After he and Beckett solve a case, he finally answers Gina's phone call and Beckett overhears him breaking up with her.
For all of his life, Castle never knew who his father was, nor did he have much interest in knowing. In Linchpin, CIA Agent and former muse Sophia Turner hints that Castle's father has a connection to the CIA when she tells him he would have never be able to shadow her for his books otherwise. She is killed right after her revelation, so Castle gets no further details, nor confirmation from Sophia's colleagues. He thinks it makes sense, given how his father disappeared out of his and his mother's life, but Beckett believes Sophia was lying, since she turned out to be a traitor who plotted to bring down the U.S. government.
In Hunt in season 5, Castle finally meets his father in Paris, when he, using the name Jackson Hunt, saves Castle from kidnappers who have taken Alexis. Jackson confirms that he is a spy (and that he pulled strings to get Castle into the CIA) and that Alexis was kidnapped out of revenge for his killing the family of one of the kidnappers. He tells him that after spending the night with Martha, an operation went bad and he had to disappear, but he has always been watching over him and his family from the shadows. Castle learns that it was Jackson who, when he was 10 years old, gave him a copy of the book Casino Royale which inspired him to become a writer. Jackson helps Castle save Alexis, but disappears leading Castle and Alexis to wonder if he escaped from France. Castle gets his answer when he and Alexis return home and find a package containing a copy of Casino Royale waiting at the loft.
In Deep Cover, Hunt resurfaces unexpectedly during Castle's and Beckett's investigation into the death of a hacker who turned out to be one of Hunt's recruits to the CIA. Initially, at Hunt's request, Castle hides his relationship to the spy from Beckett, but when he becomes the prime suspect in the hacker's murder and gets shot trying to stop an intelligence leak, he fesses up. The situation also leads to Hunt's reunion with Martha, but leaves Castle embittered by his father's constant mixed motives.
Although he never meets his father again, in season 8 Hunt's new wife, Rita, secretly introduces herself to Beckett in XX, and meets Castle in Dead Red, where she tells him that Hunt remains very proud of him.
Castle confesses to Beckett in The Wild Rover that one of his first writing efforts was a fraud, in that he paid a prep school classmate to write a term paper for him. It was so well done and Castle felt so guilty about the adulation that came his way, that he threw himself into learning how to write so that he would know he earned his fans' praise. Even after establishing a successful career and having numerous best sellers, he is still trying. He fears that Beckett will think less of him, but she tells him she likes him in spite of his insecurity.
In The Final Nail, Castle credits an old prep school friend, Damian Westlake, with starting him down the path to becoming a famous writer. Castle was sent to Edgewick Academy when he was 14 and a story about his homesickness which he submitted to the literary magazine caught the attention of Damian, the editor at the time. He told Castle he had a talent for writing and encouraged him throughout school to keep working to develop it. In Castle's words: "Without Damian Westlake, I’m a lawyer, I’m a grifter, I’m a rodeo clown, but I’m not a writer. Without him, I’m not me." Later, Castle watches painfully as Damian, someone he had always looked up to and respected, is arrested for hiring another school classmate to murder his own father.
Castle's first novel, In A Hail of Bullets, was rejected multiple times by multiple publishers before Black Pawn finally agreed to publish it. Castle keeps his very first rejection letter in a frame in his home office to motivate himself. Eventually, it becomes a best-seller and wins the Nom DePlume Society's prestigious Tom Straw Award for Mystery Literature. In Last Call, Castle tells Kate Beckett he wrote the book in a booth at a well-known bar for writers called "The Old Haunt", which dates to the 1800s, and which Castle buys later in the episode. His portrait hangs over the booth in the bar. In Lucky Stiff, he tells Beckett he spent the money he earned from the book in six months, since he was still in college and naive about money. Eventually, he figured out that the only luxury he really wanted was freedom to live his life on his own terms.
He soon follows up In A Hail of Bullets with another bestseller, A Rose for Everafter  and begins a highly successful writing career, later creating his popular series about PI-turned-spy Derrick Storm. Eventually, however, he kills off Storm and is at something of a career crossroads when he meets Beckett.
Heat Wave, his first book about Nikki Heat, the character inspired by Beckett, is a big hit. He goes on to write nine more Nikki Heat books, and their success also leads him to revive Storm in a short series of novellas. Some of the original series of Storm books are also reissued by Marvel as graphic novels.
Heat Wave was to be made into a movie, with fictional actress Natalie Rhodes (played by real actress Laura Prepon) portraying Nikki. . However, it emerges in Need To Know that Natalie dropped out of production and the film went straight to DVD, to Castle's chagrin.
Involvement with the NYPD
Castle started helping the NYPD solve crimes when he caught their attention as a suspect after several murders resembled scenes from his novels. After the case was solved Castle pulled in a favour from the mayor and was allowed to shadow Detective Beckett to do research for his book. After his first book was published Castle was considering taking on a new project but his publisher offered him a contract to write three more Heat novels.
Castle also purchased an expensive espresso machine for the Homicide Division after commenting that their coffee tasted "like a monkey peed in battery acid."
At the start of season four, Castle is initially allowed to continue working on his own at the precinct while Beckett recovers from being shot, but is eventually asked to leave by the new captain, Captain Victoria Gates. He has to ask the mayor to intervene again to get back in with Beckett when she returns (in Rise).
At the start of season six, when Beckett briefly takes a job with the attorney-general's office in Washington DC, Castle's relationship with the NYPD is paused, but he is permitted to resume his role in the precinct when Beckett rejoins the force in Number One Fan.
In the season 7 episode Bad Santa, Castle does an unwise favour for one of his old Mafia research contacts, causing such a conflict of interest that he is ordered to stop working with Beckett. He sets up Richard Castle Investigations to become a private investigator and attempts to shadow Beckett's cases while not actually working with her. The return of the serial killer 3XK in Resurrection sees him allowed back into the precinct on a one-off basis. When Beckett is kidnapped by 3XK and Castle rescues her, the DA and Captain Gates arrange for him to be "sentenced" to 1,000 hours community service for "assaulting" 3XK – the sentence to be served as a consultant working with Beckett. He is therefore allowed back permanently.
In season 8, Beckett's temporary separation from Castle (see below), and her promotion to captain, make working together more difficult, but their detecting partnership eventually survives the difficulties.
Relationship with Kate Beckett
Castle shadows Detective Kate Beckett for research, with his friend the Mayor's permission, to write his Nikki Heat series of novels, with the major characters based on himself and Beckett and her colleagues. They first meet when Beckett, who is a fan of Castle's previous works, figures out that a copycat killer is on the loose in New York City and calls Castle in to consult on the case. Having killed off his wildly popular character Derrick Storm because he got bored with him, Castle is intrigued by Beckett and comes up with Nikki Heat, in part to satisfy his publisher who has threatened legal action unless he gets started on a new book and in part to spend more time with her.
During that first case, Castle cold reads Beckett and figures out that she became a cop because of a tragedy that befell her family and for which her family was denied justice. Eventually, after he notices that she wears a man's watch on her wrist, she tells him how her mother, Johanna Beckett, was murdered, the crime was never solved, and her father became an alcoholic as a result, but eventually sobered up. Castle violates Beckett's trust when he re-opens the case against her wishes and figures out additional information. She puts an end to their partnership, but eventually takes him back after he offers her a heartfelt apology. When a random murder uncovers a connection to Johanna's killing, Castle gives the department several thousand dollars in an effort to find the person responsible for both crimes. When the case is solved and Beckett finds the man who killed Johanna, but has to kill him, Castle offers to stop shadowing Beckett out of guilt, but she refuses saying she has gotten used to him "pulling her pigtails" and that she wants him around when she finds the people behins her mother's murder.
Throughout season 2, they generally bicker and banter with each other, all the while slowly becoming friends. When a crazed fan of Nikki Heat begins stalking Beckett, Castle becomes concerned and even spends the night at her apartment, eliciting lots of comments from Beckett's co-workers at the precinct. He is able to give her just enough warning before the fan blows up her apartment and she survives. He lets her stay at his loft temporarily and for her own protection, and once the case is solved, presents her with her father's repaired watch as a gift.
However, when Beckett falls into a relationship with handsome Detective Tom Demming, Castle becomes jealous and realizes his feelings for Beckett may go beyond being just platonic. He invites her to spend the summer with him and his family at his house in The Hamptons, but she turns him down to spend time with Demming. Feeling very hurt and being behind on his next Nikki Heat book, Castle offers to leave the precinct for the summer and head to The Hamptons to write so Beckett can have her privacy with Demming. His leaving makes her realize that she has grown to care for him, so she breaks off things with Demming and resolves to confess her feelings to Castle. But before she does so, Castle reveals that he has reconnected with his ex-wife publisher Gina, who has accepted his invitation to The Hamptons.
At the end of the summer, Castle fails to call his friends at the precinct, as he promised, when he returns to town and finds Beckett and her friends furious with him. Eventually, Beckett and her colleagues forgive him and she takes him back as her partner. He finds Beckett spent the summer looking into her mother's murder and struck up a relationship with a motorcycle riding cardiac surgeon, Josh Davidson, who she eventually admits is too busy to really be there for her, but she stays with him when he doesn't go on a Doctors Without Borders mission. Having ended his relationship with Gina due to a lack of "magic", Castle begins to emphasize to Beckett how he will "always" be there for her.
When the detective who first investigated Johanna Beckett's murder contacts Beckett with additional information and is gunned down right in front of Castle and Beckett, Castle maintains his steadfast support for her, despite her urges to back off for his own safety. When Beckett's squad members, Detectives Javier Esposito and Kevin Ryan, are kidnapped Castle and Beckett share their first kiss as they pose as a drunken couple to distract a guard in order to break into the building where they are being held and save them.
Castle also helps Beckett locate a group of terrorists who plan on setting off a dirty bomb in the city, almost dying twice with Beckett in the effort, as well as travels to Los Angeles with her to solve the murder of her training officer, Mike Royce. As a result of these experiences and throughout season 3 with both in relationships, Castle and Beckett's friendship, partnership, and level of trust in each other grows stronger and their flirting becomes more heated.
That relationship is put the ultimate test when the man who arranged Johanna Beckett's murder escapes from prison and sends Beckett on a dangerous manhunt for the people ultimately responsible. When it appears that Beckett is their next target, Castle demands that she walk away from the case and, when she tries to push him away, he tells her she hides behind the case and in relationships with men she doesn't love out of fear. Beckett ends their partnership for good, but signals that she is willing to work with him again because he has always stuck by her. When assassins shoot Beckett at the funeral for Captain Roy Montgomery, Castle finally admits his love for her just before she loses consciousness.
Castle is crestfallen when Beckett tells him she doesn't remember anything about being shot, including his saying he loves her. He doesn't hear from her at all over the summer while she recovers and is furious when she finally re-establishes contact. He puts his anger aside when she tells him she broke up with her boyfriend Josh and that she cannot commit to a relationship with anyone until she solves her mother's murder. Castle agrees to help her, but when he gets a call from a mysterious man named Smith that Beckett can only stay safe if she backs off from investigating her mother's case, he convinces her to let it go. He does not tell her about Smith's contact, nor about the fact that he plans on trying to crack the case himself. He spends most of season 4 keeping this secret from her.
He hears from Smith again while he and Beckett investigate a murder that traces back to the Mayor of New York City. Smith gives Castle a clue that helps them crack the case and exonerate the Mayor, but ruins his chances of running for higher office. It also keeps Castle in the precinct, since without the Mayor, Captain Victoria Gates would have certainly gotten rid of him, where he can continue to protect Beckett. Before disappearing, Smith refers to Castle as "a well-placed pawn" that protects the Queen in a game of chess.
While accidentally overhearing Beckett in the interrogation room, Castle learns that she does, in fact, remember him telling her he loved her, and has only been pretending not to, because it was too much to deal with. He is upset and distances himself from Beckett for several weeks without explaining why, to her bemusement. Eventually, they have an oblique discussion about the issue, without ever addressing it directly, and the partnership is repaired.
When Beckett reopens the case of who shot her to protect the conspiracy that killed her mother, Castle confesses to her how Smith contacted him and how he agreed to keep her away from the case in exchange for own safety. She is furious with him, but he stands his ground, saying he did it simply because he loved her. She refuses to back down and he leaves, ending their relationship and partnership for good. He even erases the murder board he constructed of Johanna Beckett's case. But when Beckett barely survives an encounter with the sniper who shot her, Cole Maddox, and resigns from the NYPD after being disciplined by Captain Gates, she realizes all that matters to her is being with Castle, so she seeks him out, and tells him. He forgives her and they finally consummate their love for each other.
In season 5, Castle and Beckett navigate the perils of a new romantic relationship. He takes her to his house in the Hamptons, becomes jealous when Beckett must protect a handsome wealthy entrepreneur, and fights off the advances of an aggressive and attractive entertainment reporter all while working to hide the relationship from Captain Victoria Gates. The worst test comes when Castle is framed for murder by the serial killer 3XK and Beckett's team arrests him. Nevertheless, Beckett sticks by her man and eventually admits her love for him just as he did previously. As their one year anniversary approaches, Castle either is oblivious to the fact that Beckett wants to know where their relationship is headed or he is reluctant to discuss the subject. As a result, she interviews for a job in Washington, DC, leaving Castle furious that she looked into the job without talking to him first. When they meet up to talk things out, Castle shocks her by proposing instead of running away like his mother says he typically does.
In season 6 she says yes, and the couple make plans to get married. But on the day of their wedding, Castle is run off the road in his car and disappears (see Disappearance of Richard Castle). At the start of season 7 he has been missing for two months before being found, distressed and with partial amnesia, in highly unusual circumstances. This puts a brake on the wedding plans while the couple attempt to find out what has happened, and while Castle copes with his guilt at the mysterious events. Some weeks later, however, he is knocked out in a grenade explosion and experiences a vivid dream in which he runs to the precinct after apparently 'waking up' and finds that nobody there knows him because, six years ago, a different detective was assigned to the case where he and Beckett met. Realising that everyone's life has turned out much worse as a result, including Beckett's and his, when he awakens in real life he asks Beckett to marry him straightaway. She agrees, and they tie the knot at a whirlwind ceremony in the Hamptons, before having an impromptu honeymoon on a Wild West tourist ranch while investigating a case.
In season 8, Beckett learns that Bracken had a partner in his money-laundering drug-smuggling business, that the business is still thriving, and that the partner has sent at least one "hit squad" to kill her for her interest. In a dubious decision to keep Castle from investigating - and thus putting himself in harm's way - Beckett moves out of the loft without revealing to Castle the danger she herself is in. Castle, therefore, thinks he must have messed up and spends several weeks trying to "win back" her favor. By mid-season, while Beckett is still hiding her investigation from Castle, they decide to take a break from their "time-out" and have several clandestine meet-ups for sex.
Eventually, Castle and his P.I. assistant Hayley figure out what Beckett is up to; he confronts his wife about it and they come to a reconciliation of sorts. Beckett moves back into the loft and promises that when she makes any progress on the case she's secretly investigating, she will share it with him so they can take down the organization together.
In the last scene of the final episode of the series, the story flashes forward seven years to show Castle and Beckett in the loft, which is now full of toys, with their three children, Lily, Jake and Reece, sitting down for a family meal.
In addition to his two marriages we know Castle to have been involved with several women.
In A Rose for Everafter, Castle reconnects with his old college flame and first love, Kyra Blaine when they investigate the murder of one of her bridesmaids. She and Castle met in college after his first bestseller was published and they dated for three years before Kyra told him she needed space and traveled overseas. The breakup clearly left him very hurt and may be the reason why his two marriages failed. As he says in the episode, his marriages "seemed like the right thing to do at the time." Beckett describes her as "real", which is unlike Castle's two ex-wives. As the investigation progresses and Beckett begins to suspect Kyra's fiance to have had something to do with the murder, Kyra becomes confused and goes to Castle for comfort. They meet on a rooftop where they used to spend time together when they dated and share a passionate kiss. Eventually, Beckett finds that Kyra's fiance had nothing to do with the murder and truly loves Kyra, so Castle stands aside as she gets married.
Castle meets Ellie Monroe when he makes an appearance on Bobby Mann's talk show and she seduces him to try and get the lead role in the Heat Wave movie. He breaks it off when he discovers that she has also been sleeping with a network executive in order to get a role on a TV show.
When he appears in the New York Ledger's Ten Most Eligible Bachelor list, Castle dates Most Eligible Bachelorette #3, but during the date he's distracted by Beckett, who is on a date herself, and the case they're working on. Eventually, their dates ditch them and they run off to solve the case.
When Castle and Beckett investigate the murder of a man who they discover was a CIA agent, Castle is reunited with former muse Sophia Turner, upon whom he based the character of Clara Strike, from his Derrick Storm novels. He tells a curious and jealous Beckett that around 2001, he shadowed Sophia for a year for research for Clara Strike, just as he is shadowing her for research into Nikki Heat. Beckett learns later that he and Sophia did sleep together, and Sophia tells her she regrets doing so, since afterward the spark was gone. When Sophia reveals herself to be a traitor who plotted to take down the U.S. government, Beckett figures she was lying about her and Castle's relationship.
During the period at the end of season 4 when Castle is unhappy with Beckett, he shows up to a crime scene in his Ferrari with Jacinda, an air hostess, telling a bewildered Beckett he met her on a recent flight from Vegas. They go out on four dates in three days, even though Beckett correctly suspects that she doesn't seem like Castle's type. She seems to be out of the picture by the time Castle and Beckett's rift is healed in the following episode. 
Hobbies & Interests
His safe word is apples, his favorite holiday is Halloween, and he enjoys playing laser tag, guitar hero and basically acting like a child. He is fascinated by gadgetry like onion goggles and "apped" up cell phones, and generally likes to "touch things" to satisfy his curiosity..
Having written his first book in a bar, he enjoys bar culture and knows quite a bit about the Prohibition Era.
Being a writer, he also is fascinated with the occult, aliens, unexplained phenomena, and spies, all of which run directly counter to Beckett's more rational way of looking at crimes.
- He wears a Kevlar vest that he specially ordered with the word "WRITER" printed across it.  The vest finally comes in handy when Castle is accidentally shot in Number One Fan and the bullet does not penetrate the vest.
- In Lucky Stiff, he tells Beckett he worked with the Dean of the law school where Johanna Beckett taught to honor her legacy by starting a scholarship fund in her name which would give a full ride to a student seeking to dedicate their career to giving a voice to those who have fallen through the cracks of the justice system.
- He’s Dead, She’s Dead
- Nanny McDead
- A Chill Goes Through Her Veins
- He’s Dead, She’s Dead
- Anatomy of a Murder
- A Deadly Game
- Poof, You're Dead
- Suicide Squeeze
- Head Case
- A Rose for Everafter
- Flowers For Your Grave
- Nikki Heat
- When The Bough Breaks
- Hell Hath No Fury
- Dial M for Mayor
- 47 Seconds
- Undead Again
- The Late Shaft
- The Third Man
- Pandora and Linchpin
- The Limey
- Undead Again
- Flowers For Your Grave
- Tick, Tick, Tick. – (Part 1)
- Last Call
- Always Buy Retail