"Inelegant Heart" (Season 6, Episode 2)
Callen: What am I gonna do with a dog?
Sam: You can take care of it, play with it, scratch its ears. They're men's best friend.
Callen: Thought you were my best friend. Oh, you want me to scratch your ears, is that it?
Sam: A dog would be good for you.
Callen: No, no, come to think of it. I feed you, I take you for walks and you are very protective of me.
Sam: Don't say it!
Callen: You’re my dog! Huh? You're my dog!