Beckett: That's espionage.
Castle: More like sexpionage.

Beckett: Castle, if we were getting married, would you want to know about all of the men I've been with?
Castle: ALL sounds like a lot.

Ryan, why don't you take The Situation down to the bar?

Beckett

Beckett: Oh my God, that's Jenny!
Castle: Not just Jenny. Gyrating Jenny.

I'm not showing up solo when Lanie's bringing Captain America!

Esposito

Looks like Castle isn't too far off with his Jason Bourne theory.

Esposito

Castle: If you find out a man is cheating on you, how would you kill him?
Martha: Knife.
Alexis: Shoot him.

It's like the beginning of The Bachelor, but without the appletinis.

Speaking of sweet...who's your date to Ryan's wedding?

I know, we're nauseating.

Ryan

Castle: I always liked your legs, but now I respect them.
Beckett: Yours aren't so bad either. For the next police picnic, we should enter the three legged race.

If we ever get out of here, we should seriously consider joining the circus.

Castle Season 4 Quotes

Every morning I bring you a cup of coffee, just so I can see a smile on your face. Because I think you are the most remarkable, maddening, challenging, frustrating, person I've ever met. And I love you Kate, and if that means anything to you, if you care about me at all, just don't do this.

Castle

So how's the case of "the phone sex girl who knew too much" going?

Martha