I loved this moment between Derek and Meredith and their converstaion between each other espically after their tense converstation at the nursing home:
Meredith: Hi.
DEREK: [walks into elevator] "Hi. Leaving?"
MEREDITH: "80-hour limit. You?"
DEREK: "Surgery was postponed." [smiles]
MEREDITH: [pauses] "I have a dog."
DEREK: "You have a dog."
MEREDITH: "My point is, I have a dog."
DEREK: [smiles] "You have a dog. Oh, and you know what? I love dogs."
MEREDITH: "I've moved on, so don't give me that look."
DEREK: "What look?"
MEREDITH: "That look. Our look. I'm over you."
DEREK: "I'm over you, too."
MEREDITH: "You are?"
DEREK: "No."
MEREDITH: "Oh. Well, I am. Over you."
DEREK: "I'm over you too."
MEREDITH: "You just said... shut up." [smiles]

MEREDITH: "What are you doing here?"
DEREK: "There is a clinical trial to slow the progression of early onset Alzheimer's."
MEREDITH: "Okay. Me, you can screw with. My mother? No. Not acceptable."
DEREK: "I'm just trying to help."
MEREDITH: "Well, see this? What you’re doing, being dreamy? It doesn't help. It hurts me. It messes with my head. You have a wife to go home to and I'm guessing she has no idea where you are right now."
DEREK: "No, she doesn't."
MEREDITH: "That's what I thought."