Castle/WMG

Season 4 is taking place in Castle's head.
Something said by Beckett made me realize this: "Conspiracies are your thing, Castle." Considering that Castle has his own personal Deep Throat, and that the major arc of the season is keeping Beckett from finding out about the conspiracy surrounding her mother's death, it seems reasonable to think that this season is in Castle's head, possibly while he's waiting to find out if Beckett will recover from the sniper's bullet from the end of the 3rd season.

Castle's father is in some way tied to Beckett's mother's murder
Hell, maybe he IS the one behind her murder. Either way, it would perfectly tie up two of the shows biggest mysteries and cause maximum angst between the leading duo.
 * Uh...

Castle's father is Malcolm Reynolds.
Due to some insane Alliance experiment to get Serenity out of their hair, he gets sent back in time. Into the 60s or 70s.

The undercover FBI agent who was murdered wasn't so clean
I am always reminded when I look back on the facts of Beckett mothers murder, of the first castle episode I saw the second season finale. Anyways in that episode they got so focused on the, they forgot the most important part of the case, the victim. The murder of the FBI agent is what started the chain reaction. Maybe he was actually dirty but wasn't working for the mob, and when he died, that pissed someone off who was very powerful.

Alternately, Castle is a direct ancestor of Mal.
It makes more sense than time travel.

Castle's father is Caleb.
Caleb was quite the sick fuck. Serial killer, misogynist, and who knows what else. Perhaps something he did lead to Martha getting knocked up by him.

Castle's father is Buck.
In I Love Bees, a slipspace accident brought on by Forerunner tech sends a few things to 2004 Earth. This is Halo canon. So, Buck, riding on an experimental Forerunner/Human/Sangheili ship, has a similar accident. Cue him landing in the 60s or 70s. After angsting a bit, he ends up sleeping with Martha. The condom breaks and bam said the lady, she's pregnant.

Richard Castle/Malcolm Reynolds is an Immortal
Richard Castle (who or Whatever he is) has existed for centuries drifting from one exciting job to another. From crime solving mystery writer to UNSC Marine to Browncoat veteran, He witnessed and escaped the collapse of the Earth-That-Was.

The show takes place in an Alternate Universe.
It's supposed to be set in present-day NYC; but they've shown the mayor at least once, and it was clearly not Bloomberg.
 * It's not just any Alternate Universe. It's the Buffyverse! Remember how Natalie Rhodes mentioned how the Nikki Heat screenplay was made by Spike Rosenberg? Also, all of Natalie's movies have been horror/slasher. Assuming that they were all written by Spike, it looks like our favorite vampire found a job in Hollywood as a screenwriter and director of horror movies.
 * Rosenburg?? God, I hope that's a pen name!
 * This is confirmed; the fictional Hudson University shows up several times, meaning that Castle (may) take place in Law and Order and Without a Trace land. Which would make sense given the success rate shown by Becket, Castle, and ther est.
 * Does this mean Castle is in the same universe as Batman? Holy crossover, Batman!
 * Castle is Batman.

Vampires are real.
Porphyria does not work like that. People with it don't start smoking in the sunlight.
 * Artistic license. If he had just started screaming in pain, then the natural audience reaction would be to assume that he was crazy, not that he was having a biological reaction to the light. Showing the disease's characteristic skin conditions forming would not go well and would likely break the mood.

This show is supposed to be an AU sequel to Firefly, specifically for Mal/Inara shippers.
Seriously. It's like a younger, happier Mal and Inara with short, reddish hair and a gun. But the chemistry and the Slap Slap Kiss is there!

The mayor is the Big Bad of the series.
The man who commandeered the ransom money from the police kidnappings went and used the money to secure a position of power. When Montgomery said that he could have overridden the mayor's push to have Castle hang about, perhaps he was referring to more than just being the head of the precinct.
 * Jossed as of "Dial M for Murder". The conspiracy has plans that involve him never rising above mayor.

Alternative to the above WMG, The Mayor is possessed by Richard Wilkins.
In one non-Season 8 Buffy comic, it's shown that his spirit out there still. So, wanting to have power again, and avoiding the Hellmouth this time, he possesses the mayor of New York. Now he's got an entire city's worth of cops he could use for whatever he wants.

The show is supposed to be an AU prequel to Firefly.
Since it is clearly set in Earth-That-Was.

The show is a CANON prequel to Firefly.
Mal is a decendant of Castle, and the show takes place prior to the collapse of Earth-That-Was. Such as....
 * It would be great if it ended with Alexis marrying somebody with the last name "Reynolds".
 * For that matter, what exactly is Alexis's boyfriend's last name, anyways?
 * Gundamnit You stole my WMG!! hehe Just Kidding, But to stretch this guess even further the ties to both shows could go even further.
 * Castle and Kate meeting a asian suspect named "Tam" with a adopted white daughter and/or son.
 * Castle hires a high class escort named "Inara" who looks suspiciously similar to another future Inara (which would coincide with a previous Firefly WMG about her being INCREDIBLY OLD.)
 * Castle meets a new New York DA portrayed by Gina Torres (it should noted that Mrs. Torres-Fishburne is as well known for her TV Lawyer roles as she is for her sci-fi roles)
 * Later seasons referring to some large looming fictional global political or environmental crisis in mock news reports which may be the disaster that creates the Earth-That-Was.
 * Alexis will join the marines at series end and her grandchildren in the future will follow her in a literal centuries long legacy of military service, which will include a grandson in the UNSC in 2557 and ending with Malcolm Reynolds in the 27th Century.
 * Also links to both series could go in both ways there are still Firefly and Serenity comics still made (which Joss Whedon considers as canon) so a later issue could have Mal rummaging through a box of his old things and find a photo of his Great-Great-Grandfather next to a redheaded plainclothes policewoman.
 * And Even if both series were produced by different networks they can easily say that all these are merely "shout outs" to another favorite series.

Castle is Captain Hammer!
But not in the way you think.

Castle's friendship with the mayor is because he's been willing to offer his own genetic material for certain governmental experiments. Captain Hammer, Corporate Tool, is the result of one such experiment, and is an exact genetic replica of Castle, complete with womanizing, heromongering, and arrogance, with the addition of superpowers to compensate for lack of intelligence. But Hammer, as a clone, did not have the proper human upbringing that has allowed Castle to be decent under all his self-love.

To ice the cake, Captain Hammer works in Los Angeles, the major American city farthest away from New York City, just to make sure that never the twain shall meet.

Castle is Jessica Fletcher's luckiest nephew.
Most of Jessica's relations just end up being suspects for murders, or else victims of them. Castle got the creative writing genes and, well, at least half the brilliance at solving mysteries.

He has at least some of her persuasive abilities as well -- not as obviously, but that bullet-proof vest with "WRITER" written on it spoke volumes.

Richard Castle has a personal reason for being fascinated with crime.
He likes to keep it a secret, but he has a brother whose family was murdered by the mob. That brother's name is Frank.
 * No, the family got murdered by Hungarians. That also explains why Castle has such good connections.

Martha does know who Castle's father is.
Think about it. It's been stated that his father's identity is unknown, but if Martha's last name is Rodgers, why would her son have a different one?
 * Second ep of Season Three- Castle states that he changed his middle and last names, so he's Richard Edgar (for Edgar Allen Poe) Castle. His birth name is Richard  Rodgers.
 * Doesn't change the fact that she knows who his father is. Hopefully the reason why she never told him is closely linked to the WMG above.

Martha Rodgers is her stage name.
But, as often happens with stage names, she uses it all the time.

Martha's maiden name is Castle.
We have not met her husband, but we might if the fella is still alive.
 * Jossed.

Castle is not Richard's original surname.
Wait, this isn't canon? It's implied.
 * He named himself after a comic book character.
 * His mother, a Broadway actress, got a kick out of naming her son Richard Rodgers, and he changed his name just to annoy her.
 * Confirmed in "He's dead,She's dead" where he reveals his given name to be  which he changed to Richard Edgar (after Poe) Castle
 * I know its already been confirmed but Castle's later revealed twist real REAL Name is "Reynolds" but still Richard.

Lanie worked her way through med school as a dancer.
No evidence for this whatsoever, just that Tamala Jones played Crystal Diamonds in Wu-Tang Clan's Gravel Pit video. And it would be fun for Ryan, Esposito, and company to discover that Lanie has an Old Shame comparable to Beckett's teen modeling.
 * Her performance in Swan Lake is to die for...
 * Considering how freely she talked about fetishes in the respective episode (over a corpse no less), it'd hardly seems like she'd consider it an old shame. Just something she doesn't bring up because it's hardly something one brings up in normal conversation.
 * In "A Dance With Death" she mentions she wanted to be a prima ballerina as a child but had to give it up because she, ah, developed.

Lanie and Castle will hook up

 * There seems to be some chemistry between the two, and they can use this to further the Castle/Becket UST longer, with betrayal and all such things.
 * Well...

The show is set in an alternate universe,where bad judgment is the default setting.
This explains why law enforcement would jeopardize cases by bringing along a civilian to arrests and interrogations...why the city attorney and/comptroller would allow a civilian to continually be placed in harm's way thus increasing the city's liability to a lawsuit...why a writer would continually WANT to go out police investigations (wouldn't he have something better to do?)...and finally,why a very attractive police officer,who is obviously not a good investigator nor particularly intimidating would be working cases rather than be in an admin or PR job within the department.

Easiest explanation? Alternate universe!
 * Lest you forget, in the very first episode, you see Castle signing a bunch of papers which are explained as waivers and such. Presumably, the department also signed stuff and otherwise invested some sort loophole lawyering to minimize the amount of damage that Castle can do. It's very similar to the situation with embedded reporters with the military or camera crews on shows like Cops. Or for the matter, Top Gun and America's Army (the video game). Castle gets access with the understanding that he's in dangerous situations and the police department gets good PR out of it. Also, Castle is shown to have a history of 'risky' behavior and thrill seeking - he's befriended (or what have you) thieves, mob bosses, and so forth for the sake of research. Beckett and co also do not allow Castle in any truly dangerous situations if they can help it - that's the whole reason for the "You stay!" running gag; they're not telling him to stay because it's funny, they're telling him to say because he's not trained and would be a liability. As for arrests and interrogations, outside expert - it's not like only officers can be there. As for Beckett... at what point does the show show her as being bad at her job? Castle may get the more notable eureka moments but that's only because his tend to come out of left field. As shown in the episode where the department is pissed at him, Beckett had already figured out much of the case well before Castle but allowed him to 'play along' for various reasons. In addition, the show tends to favor Castle as the protagonist - it tends to follow him around rather than Beckett. This tends to make it seem like Castle does all the work when in all likelihood, when Castle is having his family moments, Beckett is doing the more mundane aspects of an investigation that don't really need Castle's help.
 * Also, the show tends to put Castle's Eureka Moments on bigger spotlight than Beckett's (they're probably funnier). In "Poof! You're Dead" they show Castle's and then immediately after when Castle's explaining it to the detectives, Beckett pre-empts him by saying that they'd already figured it out. This isn't the first time it's happened on screen either.
 * And the OP has presumably missed all those moments where Beckett and Castle pretty much have a Eureka Moment at the exact same time and end up taking turns finishing each other's sentences, thus suggesting that they're about equal in the intelligence and figuring-things-out stakes. Beckett's clearly no slouch at her job.
 * As far as intimidating, in "Knockdown", she's able to drag a heavily built man to his feet and throw him hard enough to shatter the interrogation mirror. Assuming someone isn't capable of being physically intimidating because they're attractive (or whatever) is ... silly.

The idea of a password/codeword as brought up in "Nikki Heat" will be used as a Brick Joke later on.
Or at least, brought up.

The Casting of the Nikki Heat Movie will be...
It'll never happen. Sigh. But it would unleash a global Squee of city-levelling power... right?
 * Morena Baccarin is Nikki Heat!
 * Alas, Jossed. Natalie Rhodes will play Nikki.
 * Back on the table now that Natalie Rhodes is in rehab as of To Love and Die in LA!
 * Adam Baldwin is Jameson Rook!
 * Ron Glass is Captain Roy Montgomery!
 * Gina Torres is Lanie Parish! (Lanie remarks: "I got a lot taller...")
 * Alan Tudyk is Ochoa! (Javier remarks: "I got a lot whiter.")
 * Sean Maher is Raley!
 * ::sigh:: To Love and Die in LA giveth, and it taketh away.
 * Jewel Staite is Alexis Castle!
 * Summer Glau is the first murder victim! (On the phone to her agent, she is heard to say "How come I'm always a victim in these things? Can't I just once get to beat someone up?"
 * No, no... Summer Glau is the Murderer.

Nikki Heat is a Expy of Castle's Ex-Wife and daughter
Think about it. Their both redheads and he began writing Nikki Heat novels way before he ever met Kate. Nikki is most likely a combination of the idealized attributes of Castle's ex and daughter but is mainly a hopeful idealization of what he wishes his real ex wife could be. Kate (as with many fangirls) just thinks that Nikki is just somewhat based on either her or her cases.
 * Nope. He met Beckett just after he finished his last book, killing off Storm. A few episodes later, Martha mentions that he's starting a new series...based off her. In fact, mentioned in the very first episode: Montgomery mentions that Castle has a new idea for a female detective at the end of the pilot. And if you've read any of the tie-in novels, it's pretty obvious that Nikki Heat is Beckett...except "kinda slutty," as Castle puts it.

All of Beckett's shoes were destroyed when her apartment exploded, except for her heels.
That explains why she only wears heels, which are extremely inappropriate for her job. She's living off of a cop salary and has to buy a new place, so she has no money for new shoes.

Generation Kill is Esposito's Backstory
Esposito spent four years in the Marines. He then used the GI bill to go to school and become a detective. His marriage fell through so he got as far from L.A. as he could. The NYPD was happy to get a guy with experience in First Recon, and it also explains why he always carries an M4 when they go kicking in doors, while everyone else carries Glock 19s.

The will return
This one speaks for itself. In the same way that  This case is the   This one's coming back to bite them.

Castle's father will be revealed as...

 * The one who took out the hit on Beckett's mother. It'd be the perfect story.

The Triple Killer will return...

 * And a picture of pretty, blonde Jenny will appear on the board alongside all those other pictures of pretty blonde women that 3XK's targeted.
 * Since Jenny's actress is Seamus Dever (Ryan)'s wife, it seems unlikely. Very much possible, but unlikely.
 * I agree that it's unlikely that they'd kill her off (as well as the above, it seems a little too dark for this show) but I can certainly see a future storyline where 3XK gets it in his head to target Jenny; they'd certainly be able to get a lot of mileage out of a scenario where they save Jenny but at the cost of 3XK escaping again.
 * as of "Kick the Ballistics", though Jenny wasn't involved.

The reason Castle is so fascinated by the macabre will be plot relevant and unexpected.

 * Castle goes out of his way to avoid answering the question whenever it is asked,, to the point of outright lying to Beckett. Just Castle trying to mysterious...or something darker?
 * Probably because it is a macabre that, no matter how legitimate a reason he may have, would probably make most people look at him funny. Remember, he says himself that the only real difference between serial killers and crime fiction writers is that the latter get paid better.
 * Alternatively -- and which, I believe, would a perfect subversion -- is that Castle has no deep, dark and no doubt gloriously angsty back-story event 'explaining' his interest in the macabre -- not everyone who enjoys reading murder mysteries and solving puzzles is completely fucked up. Some people do have these interests as a result of trauma or pain in their past -- others just like weird things. The reason he goes out of his way to not explain it? Because "I'm just kinda interested in this stuff" isn't really a very creative or interesting thing for a creative writer to admit.

Beckett is pregnant.

 * As of Setup, we have a very strained, hush-hush conversation between Beckett and her mainly off-screen boyfriend, with Beckett being very untalkative about it. In fact, she seems to go more out of her way than usual to avoid talking about him. Tropes Will Ruin Your Life maybe, but an unexpected pregnancy does seem to make sense (with a handy in-story inadvertent abortion plot device, even)
 * Interesting -- although one of the key points of contention Beckett seems to have with him is that Josh isn't around very much due to his various other commitments, which suggests among other things that they haven't recently had a lot of time to do the thing that makes babies. Plus, my own experience with life-ruining-due-to-TV-Tropes personally suggests we'd have seen more of the earlier Pregnancy Tropes than we currently have...
 * In "Knockout", Castle notes that Beckett intentionally enters into deadend relationships with guys she doesn't love in order to help bury herself in her work. So there may not be any more mystery other than straight forward incompatibility.

Castle's father is Sean Connery

 * Thereby explaining his love of 007 and general badassery.
 * Possibly one of the most awesome episodes of a TV show ever. Find a way to work Michael Caine in there in some capacity, and you have the PERFECT episode.
 * Sadly unlikely though, too much awesome for one world to handle

Castle's father is Lance Hastings, Martha's ex-boyfriend actor from "One Life To Lose."

 * Which makes Shawn Spencer his long-lost brother! That... actually makes a frightening amount of sense.

The writers (and Nathan Fillion) are trying to cram so much awesome into the series that they blow a hole in the space time continuum

 * In order to go back in time and prevent Firefly from being cancelled.
 * But then Nathan wouldn't have been out of a job and wouldn't have done Dr. Horrible or Castle. So... what's your Take a Third Option?
 * Joshua Jackson as Richard Castle?
 * Hm... not seeing Pacey as Castle. Or Captain Hammer.
 * Nathan probably still could have played Captain Hammer. If Firefly had lasted into 2008, it probably would have been hit by the Writer's Strike just like everything else, giving Nathan time to appear in Doctor Horrible.
 * Whedon could be in on the scheme, and make a tape for past!Whedon telling him to end the show himself in order for Fillion to make Castle. The appearance of Fillion's Mal costume is part of the message.

Alexis is going to get kidnapped.

 * I mean, come on, the pretty, spunky, yet largely innocent daughter of a volunteer homicide detective? It's just a matter of time.
 * Congratulations! Tv Tropes Has Ruined Your Life.
 * I like this one. Maybe on her way to college. Castle will be wondering why she hasn't called, Martha will tell him not to worry, but he will and then he'll find out she's missing... I really want to see this.

The ex-husband who stole all of Martha's money (pre-season) is the one who ordered the hit on Beckett
Why not?

Gates was told about Castle by the Big Bad.
Or the Big Bad had someone tell Gates about Castle in a unflattering way. There are plenty of times when Castle got Beckett into trouble that is had to explain to someone on the outside and anyway Gates didn't seem to be disposed to writers anyway (bad experience?). My guess that Gates was picked party so if she isn't in on the conspiracy she is a person who would be the perfect one to get rid of Castle for them. And since she does seem to care for the officers under her this is a nasty move on their part in an attempt to isolate Beckett.

3XK, a.k.a. Jerry Tyson is Drew from Scrubs: Med School
They're both played by the same actor, Michael Mosley. Drew has a pretty disturbing past. He was in med school years before, but went nuts and dropped out. He spent time in prison, traveled the world, worked a bunch of odd jobs, and eventually went back to med school. After that he briefly went back to prison, only to escape and pin some of his crimes on his former cellmate.

Castle is Batman.
If you have to ask why, you're not ready to know.

Castle will become a (volunteer) police officer and Beckett will be promoted to captain.
But of course, Beckett - while accepting the promotion - will refuse to move up out of field work.
 * Wouldn't a captain by definition have to step out of the field work? Doing detective's work on the side would lead to serious neglect of her real work in that point.
 * Not necessarily. She could have the rank but not the job of leading a station. Basically, they would be rewarding her for her work by giving her a higher rank and paygrade without increasing her paygrade out of the range proper for a lower rank.

Season 5 will be the final season.
Because Castle only has one more Nikki Heat book to write, as per his contract with his publishers.
 * Although if Nikki Heat is still selling well (and the author's willing to keep going of course), it's possible for the contract to be extended.

Lanie will be kidnapped, probably to keep her mouth shut about an autopsy on Body of the Week
Admit it. It would be awesome and full of Esplanie-ness.

Beckett and Alexis have a bonding moment sometime in season 4.
After all the negative buffers with Alexis worried about her dad's safety and all, their relationship needs some positive reinforcement.
 * Yay! Confirmed-ish. When, Alexis starts panicking and requires some reassurance from Beckett. Then they all go home and share dinner. Aww.

Castle Season 4 is just another Vision from the Prophets to Benjamin Sisko
So far we have Worf and Kasidy's Equivalents. Its only a matter of time until the rest appears. The Season Finale will deal with Benny Russel as Murder Suspect.

The person behind Pandora also killed Kate's mother.

 * Whoever it is needed money and had a grudge against the world. Maybe this person was even related to one of the criminals kidnapped by the dirty cops. They started demanding money out of the cops, then got more and more power from the money they'd taken.

Eventually, they found out about the professor and the plan. Using some of the money they had amassed, they set up the fake Think Tank, hired all those Mooks, and started to implement the plan. Don't ask me why, but it seemed to me like Pandora was the sort of thing that had to be done from a position of power. Who else do we know in the show who's powerful, mysterious, and evil?

.

 * The set up for that was a little too clear, and Montgomery was a little too confident earlier.
 * Probably confirmed by the fact that there's another season on the way.
 * Confirmed in some ways, Jossed in others.

.

 * It has been alluded to that Castle has some similarities with murderers. He snaps, tracks down and kills  and then is caught by the NYPD and spends the rest of his days in a mental institution where he starts imagining he's a space cowboy and Kate is a courtesan he can never truly confess his feelings too.
 * Within this further, the blues gloves represent Kate's Mum's Murder. They're the unsolved mystery that has everyone involved dying, just like the blues gloves kill all witnesses.
 * Montgomery's youth is represented by The Operative, with differing opinions on how to keep the peace.
 * Jossed.

Castle's father is a spy.

 * That was way too fascinating to just be a red herring, and it would certainly give the writers some story arc to ride on, since Castle doesn't seem likely to be canceled anytime soon, knock wood.
 * He was the one behind Pandora.
 * No, he was just mentioned as someone Sophia worked with.

The end of Season 4 will finally have Beckett and Castle hook up.
In the last chapter, Castle and Beckett will finally confront each other about their respective non-confessed feelings for each other and their issues, and, in the heat of the moment, they will end up having wild, kinky sex. The next scene will have Beckett waking up the next morning on Castle's bed.

Castle's father is Mr. Smith.
It's been hinted that Castle's father is a powerful man in the intelligence community. Smith is also apparently a powerful man.

Castle and Beckett will start a private investigation agency
.
 * Castle has enough funds to get such a venture off the ground.