Will you remember me in an hour?
Yes.
Will you remember me in a day?
Yes.
Will you remember me in a week?
Yes.
Will you remember me in a month?
Yes.
Will you remember me in a year?
Yes.
I think you won't.
Yes, I will.
(This is followed by a short pause to suggest that this is separate from the joke.)
Knock, knock!
Who's there?
See? You've forgotten me already!