Bailey Chase, who plays Will Sorenson, played Graham Miller on Buffy the Vampire Slayer, a show on which Nathan Fillion had a recurring role.
When Castle is preparing for the drop and talking to Beckett, he is buttoning his shirt. He gets to the next-to-last button and finishes buttoning it before the shot cuts to Beckett. When the shot cuts back to him, Castle is buttoning it again.
Beckett: (about the cover art to Castle's Nikki Heat book) She's naked!
Castle: She's not naked. She's holding a gun... strategically.
Sorenson: (to Beckett about Castle) You never told him how you stood in line for an hour just to get your book signed? How his novels got you through your mother's death?
Castle: Nice guy. I can see how it wouldn't work, though.
Castle: Sure. Handsome, square jawed, by the book.
Beckett: And that's a bad thing?
Castle: He's like the male you. Yin needs yang, not another yin. Yin yang is harmony. Yin yin is a name for a panda.
Sorenson: A couple dozen best sellers doesn't make you a criminologist.
Castle: I also don't need a weatherman to tell me that the sky is blue.
Beckett: Oh for Gods sakes! Why don't you both just drop your pants and get it over with!
Castle: I'm game.
Beckett: Six months.
Castle: Six months what?
Beckett: We dated for six months.
Castle: I didn't ask.
Beckett: Yea, I know. You were not asking very loudly.
Castle: I know, I'm like a Jedi like that.
Beckett: It's Sunday morning, shouldn't you be slinking home from a scandalous liaison?
Castle: Would you be jealous if I were?
Beckett: In your dreams.
Castle: Actually in my dream you're never jealous, in my dreams you just join-
(Beckett sticks the bear claw into Castle's mouth.)
(Castle is getting ready to make the drop-off)
Beckett: Be careful, okay?
Castle: Do I detect actual concern for my well-being?
Beckett: Screw this up, and I'll kill you.
Castle: That's more like it.
International Episode Titles:
Czech Republic: Ztracené děvčátko (Lost Little Girl)
Although credited Tamala Jones (Lannie) does not appear in this episode.
Original International Air Dates:
Slovakia: February 17, 2010 on JOJ
Germany: April 3, 2010 on Kabel Eins
United Kingdom: June 2, 2010 on Alibi
Finland: June 23, 2010 on Nelonen
Czech Republic: November 3, 2010 on Prima
"Get What I Want" by Bitter:Sweet
Alexis:(about her American Lit finals) I was having nightmares about Hester Prynne.
Castle: Ahh ... the irony for you is not getting an "A" would cause you shame.
This is a reference to the main character of Nathaniel Hawthorne's novel The Scarlet Letter, who was found guilty of committing adultery and sentenced to wear a prominent scarlet letter 'A' for the rest of her life.
Sorenson: Why don't you shadow a real detective?
Castle: Well, the ones on TV seem awfully fixated on their sunglasses.
This is most likely a reference to the character of CSI Horatio Caine (played by David Caruso) from "CSI: Miami" which, interestingly, airs at the same time as "Castle".
Castle: I feel like Michael finding the gun taped behind the toilet.
"Michael" is Michael Corleone, from the 1969 novel and 1972 film The Godfather.
Castle: I'm five by five.
This line was often used by the character Faith from the series Buffy the Vampire Slayer. She used it to tell everyone she was doing fine. Nathan Fillion had a recurring role as Caleb, a priest, on Buffy.