First popularized by Kojak, the 1970s TV character, this expression is now a signature line of Christoph's. The correct answer ("You do!") is implied; thus no response is necessary. The expression can be used in a variety of situations. A few common usages include: a response to a complement, a greeting, an affirmation, an expression of excitement. Be careful if you say it to your girlfriend/mistress because she might get the wrong idea.