The ending of "Deep In Death", when Castle finally works out how to win Beckett over after he's pissed her off by opening up her mother's murder case: a heartfelt and sincere apology for opening up old wounds and betraying her trust.
In "Inventing the Girl", Castle flirts with Rina, a young model who is clearly nursing something of a crush on him — until Alexis tells him that she's Katrina, an old babysitter who "did the ugly-duckling-became-a-swan thing and became a model". Castle comes in for a bit of teasing and a few disapproving comments when it looks like he's planning to hook up with her anyway — until at the end when he reveals he's actually been putting her back in contact with Alexis, because he was concerned that, like the model who was the victim of the week, she might not have anyone to turn to for support if she needed it:
Castle:: Colour me shocked, but apparently the modelling world isn't all sexy clothes and fun parties. It occurred to me that if Jenna McBoyd had had someone looking out for her a little bit she might still be alive today. So if Rina needs a friend, she knows she's got one. Martha: Oh, my son — the big softie. And don't worry, I know you have an image to protect, your secret's safe with me.
Also a bit of Fridge Brilliance: All the teasing stopped once Beckett revealed that Rina used to be Alexis's babysitter. They understand perfectly that it'll never happen and why.
There's a nice bit of father/daughter bonding in "Famous Last Words", as Castle consoles Alexis over the murder of her favorite singer.
Alexis and Beckett get some nice moments together in "One Man's Treasure". In the B-plot, Alexis spends a day working in the dead case room as part of a school careers project. While cataloging evidence in past solved crimes, Alexis finds a photo album and becomes mildly obsessed with finding its owner. By the end of the episode she succeeds, prompting Beckett to congratulate her on her detective work.
Another one, after they find the man who killed Beckett's mother—and are forced to kill him before he can tell them who hired him. Castle goes to apologize for costing Beckett her shot at finding out who ordered the hit on her mother, and says that he's through with this exercise. Beckett tells him that he has nothing to apologize for, as he was the one that allowed them to find the actual killer in the first place, and that she doesn't want him leaving, as he makes her high-stress job easier to deal with and also that "I've kind of gotten used to you pulling my pigtails." The grade-school metaphor just made it the cutest moment ever.
Castle/Beckett shippers rejoiced everywhere.
Just the fact that Castle jumped in and provided the $100k needed to draw the hitman out, just to give Beckett the chance to find her Mom's killer. He didn't even think about it: as soon as it was clear what was needed, Castle was ready to provide whatever he could to help her.
And again in "...Boom", where Beckett's apartment has just gotten blown up. Ordered to go home, Beckett retorts, "I have no home!" Castle, sitting behind her, just says calmly, "Yes, you do." No argument, no long speech - just a simple statement of "Of course you're coming home with me, how could you ever think otherwise?" Beautiful.
"Den of Thieves" goes a bit more into Esposito's backstory, and involves his old partner Ike Thornton. Near the end of the episode Ike has taken a bullet and while Esposito sits with him, he introduces Ike to his team:
"This is my partner Ryan...and this is my other partner, Castle."
The bit where Ryan tries to follow Esposito claiming they are together "...till the wheels fall off".
In what doubles as both a Crowning Moment of Awesome and this, Ike Thornton stands by his old partner Esposito and watches the 'untouchable' man who had ruined his life marched through the Precinct to the applause of the whole station, dead to rights on evidence that Ike himself secured. He's then told he's free to go, and reunites with his wife and son while the team watches on. The awwww factor is perceptible.
At the end of "The Third Man": Beckett and Castle finally go out to eat together, and she's holding onto his arm and twirling her hair in a schoolgirl way. Which Castle had noticed previously she did when she was speaking on the phone with a guy she liked and was going to have a date with.
He's Dead, She's Dead. Martha Rogers: "Richard. Whatever mistakes I've made in my life... I raised a good man." It looks like Castle's tearing up a little after that.
The entire climax of "He's Dead, She's Dead": both with Castle telling Beckett his real name and Castle comforting his mother after the loss of Chet.
At Castle's book release, he tells Beckett: "I meant it. You are extraordinary." The smile that lights up Beckett's face is absolutely adorable.
The end of Anatomy of a Murder. Giving the cute couple burgers in jail because their love story was worth it, and Beckett telling Castle she'd get him out of jail.
Also, when reading the suspects' love letters, Castle accidentally says "I love you" to Beckett, resulting in an adorably awkward moment between them.
Beckett saying she'd get Castle out is made even better by the fact that earlier, Martha had called that (breaking a loved one out of jail) an act of true love and asked him if he'd do that for Gina. Plus, the look on Castle's face is priceless.
The end of "3XK" where Castle and Beckett hold hands after Castle's near-deadly brush with the Triple Killer. It was an amazingly sweet moment to end on, especially considering how dark the storyline became.
The closing scene from Last Call, where everyone goes off for a celebratory drink together, singing Billy Joel's "Piano Man."
Notable because the drink in question is a bottle of whiskey worth thousands, and Castle spent a large portion of the episode obsessing over getting his hands on a bottle. When the Mayor agrees to sell a bottle to Castle in exchange for a sizable donation to the Police Benevolence fund, Castle pulls out his checkbook, but then insists that his friends share the bottle with him.
In "Nikki Heat", one of the minor subplots involves Ryan's nerves about how to propose to Jenny, and the tension that arises between them after a misunderstanding involving part of his plan. At the end of the episode they not only make up, but he spontaneously pops the question in front of the entire precinct and she accepts, of course. It even made Beckett tear up.
Not just Beckett. Look carefully and you can see Esposito wiping his eyes.
The scene is even more adorable when you remember that Jenny's actress is Seamus Dever's real life wife.
The end of "Poof! You're Dead". Beckett handled Castle's break up with Gina in the kindest, classiest way possible. What a sweetheart.
In "Famous Last Words", we meet Skye, the bitter, jealous, drug-addicted sister of murdered rock star Haley Blue. Haley had tried to help Sky get off the drugs just like she had, but Sky had always rejected her, partly because Skye was convinced that Haley was still using. Beckett informs her that Haley was actually 100% clean at the time of her death, and later, Beckett and Castle come across Skye in her usual hangout, apparently drugged up — but she's actually suffering withdrawal symptoms:
Skye: [Her sleazy ex-manager] gave us a signing bonus. He told us a place we could fix for cheap. I couldn't do it. No, Haley didn't want me to. [She holds up a crumpled heap of cash] I'm clean. She's gonna help me, right? Wherever she is? She's looking out for me, right?
Beckett: She's already doing it.
Pretty much every single thing Castle does in "Knockdown", from bringing Beckett flowers after she gets kicked off her murder case to taking down the shooter with his bare hands. Fuck yeah, Richard Castle. Seriously, this episode is pretty much one scene after another of Castle proving that there's nothing he wouldn't do for Beckett.
Beckett: I need you to do something for me. Castle:(automatically) Anything.
The very end of "Lucky Stiff," where Castle finally figures out what Beckett would do if she won the lottery: honor the memory of her mother. So he decides to set up a scholarship trust in her mother's name. And it is awwwwwwww-some.
Even better because at first it looks like she is going to be pissed because he can't stay out of her personal life, then she smiles, says thank you, and is almost moved to tears.
Which is a good call back to the end of season one and how far they have come together. She now knows that these impulsive intrusions aren't because he is a rich idiot but because he is a nice guy that just likes seeing people smile. It's also likely that she never gave the idea a great deal of thought since she never expected to have the ability to do something like this, and Castle knows her well enough to figure out what her secret wish was.
In 'The Final Nail', Beckett questions why Castle trusts an old friend so much, even though all the evidence in their current case points towards the old friend. Castle talks about how when he was at boarding school, new and alone, the friend in question read a story Castle wrote about being alone. The friend published the story in the school paper, told Castle he had a great gift for writing, -something Castle hadn't heard before- and generally critiqued and advised on Castle's work. Which, given that Castle wrote his first bestseller in college, must have been a crucial time. It was a really emotionally naked moment for Castle - writing isn't just a job; it is who he is.
Doubling as a 'Set Up' - Castle intially helps Alexis get out of going to a spa with her grandma. Later, Castle learns that there maybe a dirty bomb aboard in the city. He sends Alexis off with her grandma, with a 'It'll be good for you.' The way his benevolent face freezes when she turns away, with tears welling up in his eyes, makes it clear Alexis is the single most important thing in his life. The rest of the detectives describing how they tried to do the same with their significant others also count.
Indeed, kudos to both actors. You can tell Alexis is confused and angry and wants to ask (but doing so would hurt Martha's feelings). Castle wants to tell but doing so would panic Alexis and Martha. And when Alexis goes upstairs, you can tell Castle wants to say "I love you" in case this is the last time they get to see each other but that would -also- give away that something is really really wrong.
There are quite a few of these in 'Countdown'.
When Castle and Beckett hug after the bomb does not go off. Also when they were locked in a freezer together.
Then Esposito, ex-military, emphasizes that they don't know how lucky they were. Castle looks at Beckett and says, "Yes. I do."
The end scene of "Law and Murder": earlier in the episode, Castle has noted that Forbidden Planet, a favourite movie of his, is playing at a nearby cinema. At the end, Beckett casually mentions that she's planning on seeing it. Castle lets her believe that he's never seen it before to give Beckett the opportunity to 'educate' him about one of her favourites for a change (and, of course to accompany her in seeing it).
The small part in the poker scene in "The Dead Pool" when Dennis Lehane tells Alex Conrad that he couldn't sit at one particular chair because said chair was where the late Stephen J. Cannell sat. As a tradition, the chair is empty for a year. Note too that one of the reasons Alex started to move to the chair is because the group set up a drink and a stack of poker chips for Stephen as if he were still coming to play. The camera also lingers conspicuously on the empty chair when Alex moves away rather than on Alex himself.
The end of "The Dead Pool" when Castle reveals his jealousy outright to Beckett and Beckett declares that she's a "one-writer girl." The last shot of the episode is with Beckett and Castle hanging out at the precinct together. Not just any shot but they're sitting at one of the most commonly used establishing shots in the series - Beckett at her desk with her back to the camera, Castle sitting at the chair to the side. Preceded with a shot of Castle basically just staring fondly at Beckett. Mirroring and as with the poker scene above, much of the effectiveness of the scene isn't in the strict action or dialogue.
Beckett reading the last paragraph of Royce's letter then turning to watch Castle sleep on the flight back from LA to NY. Not to mention when she changes her mind in LA and goes back out of her bedroom to find Castle after they share an electric moment only to find him gone.
Most of the scenes in "Knockout" are of the Tear Jerker variety, but the moment when Martha grabs Castle's hands and tells him not to waste another minute holding in his feelings for Beckett is one of the sweetest, most heartfelt moment in the show's entire run.
Also, in a way, the ending; Montgomery cares deeply enough for Beckett to sacrifice himself to protect her, Castle cares deeply enough for Beckett to bodily carry her away from danger (and then apologise for doing so) and then, when Beckett's been shot and Castle confesses that he loves her, it looks very much like Beckett is trying to smile at him before she loses consciousness.
In "Nanny McDead", Castle remembers when Alexis was five years old and he brought her to the park every day. And he shows a photograph of the both of them walking towards the park to Beckett. It is a very cute moment, the first time it is shown how much Richard Castle loves his daughter.
It's a low-key moment, but the bit in the pilot where Castle is discussing the case with Alexis and they're playing around, which ends with Castle pushing her down the hallway as she leans back against him. It's only the second time we've seen them interact, but it's an early indication of how close their relationship is.
When Alexis catches Castle watching videos on the dominatrix website in "The Mistress Always Spanks Twice." Castle's fumbling attempts to close his laptop and explain himself are priceless.
At the end of "A Deadly Affair", when Castle and Beckett turn around and realize what's happened. Could also double as a Crowning Moment of Awesome.
In Season 4's "Heroes & Villains", the journalist that writes and draws the "Sword of Lone Vengeance" comic decides to take the heat for the Lone Vengeance killing of the victim, believing it was his girlfriend, an officer named Hastings. When it is finally discovered who did it, the journalist and the officer leave the precinct and kiss as the elevator's door closes. Castle compares the journalist and officer with himself and Beckett (someone who earns his pay through writing and his policewoman muse whose adventures he writes about) and the detective smiles at him as he leaves.
Castle and Alexis bonding over father-daughter movie time during "Demons", and the heartfelt advice he gives her over relationships and specifically about her and Ashley. Made of d'awwwwwwwww.
Not to mention that when the police are storming the ruins of the bank, until she sees him Beckett only yells out "Castle!", making it very clear that for all the innocent people in that bank, at that particular point of time there is precisely one person who she gives a shit about. When they're reunited, well... ain't nobody else in the world. Martha has to gently remind Beckett that yes, there are people who are not Castle in that bank.
Martha and Castle get a nice moment when the hostages are being herded into the safety deposit box vault and there's a very real possibility (for the characters, anyway) that everyone will die:
Basically, everyone but Ryan and Esposito gets a chance to act their butts off during the episode, is the idea.
They both at least get a CMOH though, when Beckett alerts them to the robbery. Ryan is initially reluctant to act, because their department only does homicide. The second he and Esposito learn Castle is in the Bank, they immediately kick into action.
There's also Martha's conversations with the pregnant woman and the bank worker she'd been arguing with at the beginning of the episode.
Not to mention when the hostage takers' leader is threatening Castle's life, and the absolute fury in Beckett's voice when she tells them that if they even come close, she will personally storm right in and put a bullet through his skull.
Everything that happens between Beckett and Esposito during "Kill Shot."
The moment betweeen Castle and Beckett at the end, when she thanks him for letting her have the space she needed.
In "Cuffed", Gates remarks that two of her people are missing. She's definitely warming up to Castle.
Everything involving the dog in "An Embarrassment of Bitches".
The last ten minutes of "The Blue Butterfly." Kate's face says everything.
The last scene of "Linchpin". In this chapter and the previous one, Beckett has clearly felt disturbed after hearing that CIA agent Sophia Turner was the inspiration for a character in Derrick Storm's books, that Castle slept with Sophia and that the relationship between Castle and Sophia got screwed up as soon as they slept together. Castle later tells her that the character based out of Sophia actually ended up being more like Beckett, which is why he chose her as her muse. In the end, Beckett playfully bumps into Castle, showing that, perhaps, there is still hope for them.
"Always". Holy hell.
Castle: Beckett, what do you want?
Beckett: You. [she kisses him] I'm so sorry, Castle. I'm so sorry. I'm so sorry.
Castle: What happened?
Beckett: [The man who shot me] got away, and I didn't care. I almost died, and all I could think about was you. I just want you. [cue The Big Damn Kiss]
Earlier, Alexis delivers her graduation speech as her father listens:
But just because we're leaving, and that hurts, there's some people who are so much a part of us, they'll be with us no matter what. They are our solid ground. Our north star. And the small clear voices in our hearts that will be with us...always.
The last scene between Castle and Alexis in "Secret's Safe with Me" in Alexis' new dorm room, when she asks her father to "do it" one last time. The "it" in question? Checking under her bed for monsters, just like he did when she was little.
The handshake kiss. Goddamn it. What a way to make hearts stop beating.
Despite finding out about the identity of Beckett's secret boyfriend, Ryan keeps his mouth shut when Esposito complains about his lacklustre results in finding out the identity of Beckett's boyfriend in "Murder, He Wrote", simply because Ryan realized it would be unfair to Beckett if they stuck their noses in too deep in her personal life. D'aw!
Better still when you remember that in the previous episode Beckett had worried about Alexis knowing about their relationship because 'She'll tell Lanie, and Lanie will tell Esposito, who will tell Ryan, and he's the biggest gossip in the station.' Well, Ryan's found out and he hasn't even told them that he knows.
Also remember that he's the most rule abiding one among them. He surely knows/realizes the same thing they do - that they could very well be called up on a ethics violation if their relationship is public. So despite knowing this and despite his rule abiding nature, he'd rather see them happy and together and not suspended than follow the rules. He also probably realizes that since he found out on his own and no one knows, he can either help them or use plausible deniability to help them.
Extra heartwarming: in "Probable Cause", after proof starts pointing out towards Castle, Ryan decides to tell Esposito, but he also adds that he is only doing it because of the current circumstances.
"Probable Cause", season 5's first dramatic episode since its opener, gives us a scare when Castle is pinned as the prime suspect, with overwhelming evidence pointing towards him despite his innocence. Naturally, Beckett, Ryan, and Esposito know that something is wrong, but they're not alone. Gates is just as desperate as the trio in their attempt to find evidence to implicate 3XK as the real perp framing Castle. This despite the way things turned out between her and Castle in "Secret's Safe with Me" over the dolls.
The sheer fact that Beckett, although she is confronted with some pretty significant evidence of both, ultimately never once loses faith that Castle is neither responsible for the murder nor cheated on her with the victim. Particularly in light of the fact that a running subplot in the episodes leading up to this one has been Beckett's insecurity over Castle's previous relationships with other women and, given the evidence she's confronted with, there's not a person alive who wouldn't understand why she might choose to think the worst of him. Even Castle acknowledges this.
A little one: when Ryan and Esposito are starting to investigate Castle's calls, Beckett starts to tell them that they may find something, but both of them tell her they know about them, and do not make much noise about it, because they know how important it is for Beckett.
Beckett's explanation for her love of the much mocked Nebula 9 in "The Final Frontier" leaves Castle (and viewers) water-y eyed. The whole episode her boyfriend, coworkers, and even the actors of her favourite short-lived sci-fi show mock and berate it, but that doesn't dissuade her from loving it.
For much of "Swan Song" Beckett is paranoid that the unwanted documentary crew thrust upon them by City Hall might capture evidence of hers and Castle's relationship. She mostly stays in the background while the others ham it up in front of the crew—however, Castle seems to divert most of his attention in making Beckett shine (as opposed to, say, competing with Espo for the spotlight, as one would think of Castle). Eventually she grows used to their presence, which comes in handy later when she and Castle successfully convince the crew to get rid of any footage that would expose her and Castle's secret relationship, including a bail out at the end of the episode with an impromptu jam session during a private meeting with a very cross Gates.
Castle naturally hams it up in front of the cameras when given the chance, but that's just him being a slightly more heightened version of how he is anyway. Aside from a brief shilling of his book, however, everything he says is about how incredible Beckett is.
"I just want them to see what I see."
Having spent most of the episode competing over the cameras, both Ryan and Esposito insist that the other deserves all the credit for their role in the big break in the case.
In "Secret Santa", Castle feels a bit let down because Alexis made plans for Christmas Eve with a boy (thus missing their traditional dinner), and Beckett volunteered for the Christmas shift. Beckett tells him that she does it because, ever since her mom died, that year's presents remained unopened, and neither her dad nor her felt up to celebrating, so she spends Christmas working to help other people. In the end, Alexis tells Castle that she cancelled her plans to stay with him, but he tells her that he knows traditions are not that important, and starts to leave to stay with Beckett, but when he opens the door Kate is already there, ready to spend Christmas Eve with him and his family. They then kiss softly in front of the tree.
The end of "After Hours"; having spent the entire episode bickering, when they're reunited at the end Beckett is so relieved to see that Castle is unharmed that she runs and leaps into his arms.
Beckett: (whispers) I thought I lost you.
Castle: No, never, never.
Javier going above and beyond the call of duty in order to help Joey, a 14-year old kid who was already caught up with a man capable of and willing to murder those who have outlived their usefulness, turn away from a live of crime.
Beckett's gift to Castle for Valentine's Day. It's a drawer she's cleared out for him in her apartment, evidence of how she's letting him further into her life.
In "Target", when Beckett hugs Castle after Alexis has been kidnapped. When Castle warns her that the others could see her open show of affection, she answers, "I don't care."
Gates, for all her problems with Castle, puts the full force of her department to find Alexis in no uncertain terms.
In "Hunt" Castle's father reveals that, although absent for most of his life, he followed him and Alexis and was always proud of Castle. He also had more of an influence on Castle's life than Castle knew, once steering him towards the book that led Castle to want to write (Casino Royale) and helping Castle gain access to the CIA for his Derek Storm research.
The end of "Scared to Death", where we learn the #1 item on Castle's bucket list: Be with Kate. Beckett is obviously deeply touched and moved by this.
"The Wild Rover": Jenny's pregnant!
Castle's reaction to finding out the murder he'd thought he'd witnessed was actually staged by Beckett as a neat birthday surprise. It made him cry! And then there's the fact that Beckett and everyone—yes, including Gates—went out of their way to do this for Castle, all because he'd broken his leg skiing and had been stuck at home for two weeks, sad he couldn't help solve any cases.
Castle staying with Beckett when she accidentally stepped on a bomb in "Still."
The entire station's reaction when Castle confirms Beckett's safety.
Gates telling Castle & Beckett that she's fully aware of their relationship, but she had remained silent over it maintain plausible deniability. After seeing Castle & Beckett spending the entire season worried about Gates splitting them up if she found out they were now a couple due to her policies on inter-office relationships, the looks on their faces after Gates told them she'd already figured it out & wasn't bothered about it was the perfect pay-off.
Dr. Warburg's story about why completely autonomous drones are a bad idea. A drone pilot was about to blow up a car...before he saw roses on the hood and realized the car contained a pair of newlyweds. He says the human factor is necessary because only humans can "see roses." And Warburg has a rose as his desktop background.
Castle's proposal. It's not "Me or the job", its "Whatever you want, I'll be there, and don't use this offer as an excuse to break up because you're scared. I love you, you love me, and we went through too much to let you walk away like this."
And then Beckett says yes.
In "Dreamworld", when Castle is infected with a mysterious toxin and has only a few hours to live, he asks Beckett's partner how she's doing at her new job. He's glad she's doing well because that means she'll be okay without him. What were potentially his last thoughts were of her.
From the end of "Watershed":
Castle: Katherine Houghton Beckett, will you marry me?
In "Need to Know," Castle and Beckett realize that having a long-distance relationship is proving much harder on them than they thought...and then Castle hands her the solution to their problem: a key to their new DC apartment. Drop everything he's known for years to be with the woman he loves? Doesn't even need a moment to think about it. Which just makes Beckett's firing from the FBI seconds later hurt justthat much more...at least until the next episode, as shown below.
From "Number One Fan", Ryan and Esposito are about to interview a very rich man with powerful connections, but Gates steps in.
Ryan: Sir, this is our case!
Gates: Yes, and it'll be your jobs if there's any blowback. I am not gonna have you two risk your careers.
The same man later reconnecting with his long lost daughter, who he'd been separated from for 30 years.
It has to be said that Castle is the one who reunited the two. In spite of everything Emma did, he was still kind to her and wanted her to enjoy her late boyfriend's birthday present either way. Richard Castle is a truly sweet man.
And the crowner: When Beckett is reinstated as a detective, the whole precinct rejoices, Gates with them.
Gates is also happy to have Castle back too, so long as he and Beckett keep their relationship professional while on the job.
"Like Father, Like Daughter": Castle and Alexis making up after Castle was mean to her boyfriend Pi.
The suspect who took the blame for a murder for his brother (who was also innocent) reuniting with his family as a free man.
Alexis thanking Beckett for her help on the case after Beckett wondered why she didn't contact her in the first place and worried that she'd never truly be a part of Castle and Alexis' family.
"A Murder Is Forever": Remember back in season five, when Beckett and Castle went to the Hamptons? Well, they went walking on the beach, and collected some seashells... which are now proudly displayed on the wall inside 'their territory'. Castle kept them all this time.
Beckett and Castle taking care of the baby in 06x10. Every. Single. Scene.
Also, when the TV presenter's family finally comes together.
Ryan telling Jenny, if their baby was a boy, to name him "Javier," obviously after Esposito.
When Ryan and Esposito get out of the fire, Beckett and Castle run to hug them (with a CMOF when Castle jokes about their smell), and then they lead Ryan and Espo to the ambulance where Lanie and Jenny are with newborn Sarah Grace Ryan.
The end of "Smells Like Teen Spirit", where Castle and Beckett finally manage to attend their prom.
A little earlier in the same we get one from the girl who much of the episode revolved around: She enters the prom, looking more than a little nervous, until she sees the boy who had done so much to help her (he rigged special effects or maybe used hisPsychic Powers to scare the girls that were bullying her, and had to work for the lead mean girl once she figured that out). What does she do? She runs over to him and gives him a very sweet kiss and holds his hands, showing that really appreciated what he had done. Very sweet, especially for anyone who was something of an outcast in school themselves.