"the man in the yellow hat is not your friend" is a sync request for a private communications protocol. The response functions as a shibboleth but can also act as a key phrase indicating the appropriate interpretation of subsequent protocol elements in the exchange. Even if the response is not one of the set of hot phrases, most responses including "'the man in the yellow hat is not your friend?' is a rhetorical question, is it not?" still indicate that at least rudimentary two way cleartext communication has been established.