I once had a user email the help desk, explaining in a rather twisted and confusing way his issue. He signed the end of it with "shibboleet" (xkcd reference). I called him, because there was no way I'd be able to go over it through email, and for nearly an hour we totally nerded out over it together, working through it. At the end of our conversation, he said he couldn't believe the shibboleet thing was real! I confessed that I was first level and he'd happened to have asked about a thing that was of personal interest and hobby of mine... and catching the reference was the icing, that I wanted to play along.