Amy: Maybe you'll love living alone.
Sheldon: I don't know. Perhaps.
Amy: And if it turns out you don't ... you and I could live together.
Sheldon: You and... Oh, sure. And while we're at it, why don't we get engaged, too? Why don't we get a little house, start a family? Enjoy our sunset years together? Do you hear yourself, woman?!
Amy: Sheldon, it was just a thought.
Sheldon: No. Here's a thought. You're not moving in, Leonard's not moving out, everything stays exactly the way it is.