For those who must live and work among them, the next couple of months will be a challenge. Beginning this Sunday, these loyal subjects will return to Muggleshire, or Rivenmoore or wherever it is that HBO's "Game of Thrones" is supposed to take place. Prepare yourself for loved ones and co-workers shocked, outraged and generally agitated by the imaginary things that happen in this magical land that never existed. Of all the successes HBO has enjoyed with its hour-long dramas, "Game of Thrones" is perhaps the most surprising. Who could have foreseen that fantasy, a genre that suppresses the horrors of middle school by escaping into the womb of Middle Earth, would emerge as the ratings champion of premium cable?