"Watson: Don't do that
Sherlock: Do what?
Watson: The look
Watson: You are doing the look again
Sherlock: I can't see it can I? It's my face
Watson: Yes and it's doing a thing. You are doing a "we both know what´s going on here" face
Sherlock: We do
Watson: No, I don't. which is why I find the face so annoying"
Sherlock, The Reichenbach Fall.