Sheldon: (on the phone) Hello, Amy. (stammers) What do you mean, where am I? I'm in my office.
Amy: No, I'm at your office and you're not here. I thought I'd surprise you with dinner.
Sheldon: For future reference, the best surprises are the ones I know about three days in advance.
Amy: Where are you?
Sheldon: It's a surprise. Doesn't feel so good, does it?