"Well, he fooled the System, didn’t he? It’s a fad among the young tearaways of the faculty at the moment—and I’d just like to take a moment to point out how remarkable it is that we have tearaways at all—where was I? Oh, yes: it’s a fad. They noticed that the System tags cultural references in your dress, and after they’d played with it for a while they discovered that there’s a narrow band of uncertainty where you can dress as—well, as Charlie Chaplin in The Great Dictator , for example—and the System will miss one tier of reference and draw the wrong conclusions. So what they do now is try to find enormously offensive things they can dress up as which they can then shade into something humans read as utterly benign but which still gets red-flagged by the System, demonstrating that machine parsing is imperfect. Well, everyone knows that, so it’s perhaps redundant, although the reminders can be somewhat spectacular. I encourage it, of course."