Ryan: Guy in a tree; Mom and Dad bickering. Seems like old times!
Esposito: Mm-hmm!

Ryan: Still no luck with the curse, huh?
Esposito: Look on the bright side, Castle, you die, your book sales skyrocket.
Castle: Great.

Suspect: Hey look, it's her! (pointing at a picture)
Beckett: You're sure this is the woman who rented the room?
Suspect: Yes.
Beckett: Rebecka Strong. She's a lab tech at the company.
Castle: Mmm, she's got cruel eyes. I bet she enjoyed watching Wilder suffer...

[A murder calls Castle away from an ad-hoc play rehearsal with his mother]
Alexis: Take me with you!
Castle: To a crime scene?
Alexis: It'd be educational. Please?
Castle: Find your own hiding place.

[After a SWAT team breaks into an apartment]
Esposito: Where's Nidal Metar? Shakir Nidal Metar! Where is he?
Tenant: There's no Shakir Nidal Metar here! Only Sally Neidermeyer!
Beckett: Ma'am, did you send a package by bike courier this morning?
Tenant: Yes, I did!
Beckett: "S. Nidal Metar?" S. Neidermeyer! Some bozo at the courier company wrote the name wrong.
Castle: Our bad. Uh, we can -
Ryan: - Yeah, we can fix this.
Castle: [lifting the door] Sorry.
[They screw the door back into its frame]

[after accusing a suspect with a lot of evidence]
Beckett:So you can play dumb, or you can play ball.
Castle:Pun intended.

[After Beckett discovers that Castle placed a bet with Esposito and Ryan over who would solve their murder first]
Castle: Listen, I'm sorry. I know it was wrong, I just-
Roselyn: Beckett, you are never gonna believe this.
Beckett: Oh, the bar on "unbelievable" is pretty high right now.
Roselyn: The vic's husband took out a three-million dollar life insurance policy on his wife last month.
Beckett: [to Castle] $100 on us.

[after being told they were investigating someone's trip to Cuba]
Beckett:I don't know...me in a swimsuit under the hot, blistering sun.
Castle:I'd be happy to rub lotion on you.

[after hearing Castle comes from a line of mind readers]
Beckett: Con artists and circus people, huh?
Castle: Yeah, and mind-readers.
Beckett: Really? So tell me what I'm thinking.
Castle: Ah! You're... You're thinking... You don't care and you want me to stop talking?
Beckett: Ooh, that's uncanny.
Castle: It's in the blood.

[after meeting Joe Torre]
Beckett: That was Joe freaking Torre!

[After Ryan and Esposito catch a break in their case]
Castle: I've got a bad feeling about this.
Beckett: Are we really rooting against solving a murder?
Castle: Well, I don't want to shave my head! Do you?
Beckett: Why would I shave my head?
Castle: You're in on the bet, aren't you?
Beckett: Yeah, but I didn't realize-
Castle: [imitates electric razor]

[as Det. Beckett speaks with the victim's sister]
Castle: How does she do that?
Montgomery: Better than anyone I know.

[Beckett has discovered who killed her mother, only to have to shoot him to save Castle's life]
Beckett: It wasn't your fault, you know.
Castle: I overstepped. I came down here to say that I'm sorry... and that I'm through. I can't shadow you any more. If it wasn't for me --
Beckett: If it wasn't for you, I would never have found my mom's killer. And some day soon I'm gonna find the sons of bitches who had him kill her. And I'd like you around when I do. And if you tell anyone what I'm about to say there's gonna be another shooting, but... I've gotten used to you pulling my pigtails. I have a hard job, Castle, and having you around makes it a little more fun.
Castle: ...Your secret's safe with me.

[Beckett, Ryan, and Esposito are at dead ends in their respective cases]
Beckett: We'll start over. Fresh eyes. You take our murder, we'll take yours.
Esposito: All right.
Castle: [a thought strikes him] Whoa, whoa, whoa, whoa. Say that again.
Beckett: You take our murder, we'll take yours.
Castle: Could it be that easy? You take mine, I'll take yours.
Esposito: What are you getting at, Castle?
Castle: Strangers on a Train.
Ryan: The Hitchcock movie?
Castle: I'm partial to the novel by Patricia Highsmith, but yes. We have two strong suspects, but with airtight alibis, right?
Esposito: Right.
Castle: We know they're connected. What if the connection is the killers?
Beckett: Jason and Eric committed each other's murders.
Castle: And made sure they had an airtight alibi for the murder they knew they'd be suspected of. It's not our victims that are connected, it's our murderers. Crisscross!

[Castle enters the room, dressed as Mal from Firefly]
Alexis: Hey.
Castle: Hey... I was just trying on my Halloween costume.
Alexis: What exactly are you supposed to be?
Castle: Space cowboy.
Alexis: Okay. A: there are no cows in space. B: didn't you wear that, like, five years ago?
Castle: So?
Alexis: So, don't you think you should move on?
Castle: I like it.