This happened in a dream I had.  We were at a large round table having dinner.  I was talking about pizza and saying something typically smart-ass about how to make good crust.  Krugman was at the other end of the table and overheard.  He jumped in just long enough to reduce my pizza thesis to mere crumbs.  The rest of the guests looked on in pity.

When the party was over, I bumped into him again on the way out.  We had this little conversation:

Krugman:  When.

Jeff:  When what?

K:  No.  When, dude.

J:  I don’t understand you.

K:  I am saying goodbye.

J:  That’s how you say goodbye?

K:  It’s like instead of saying “see you later,” people say just “later.” you’ve heard that right?

J:  Yeah but you said when.

K:  Same thing. I could have said “when we meet again,” but I just said “when.”

J:  But nobody says that.

K:  They do now.