They obviosuly have to be slightly bizarre in order to make it a challenge for the participant to steer the conversation towards, say, Lucrecia di Borgia or something similarly non-usual during polite carriage conversation... And as always, double-entendres is a great hit with the audience! But they also have to be fair, just like the two players actually have to make sure that they don't just steam-roll the other person, but have a normal (sort of) conversation that just takes a lot of strange twists and turns...