This afternoon, millions of fez-wearing fans around the world will tune in to a very special episode of Doctor Who. The venerable British sci-fi series turns 50 today — though the time traveling alien Doctor himself is probably somewhere on the wrong side of 1,000.
From scrappy, low-budget beginnings (bubble-wrap monsters, anyone?), Doctor Who has become a global phenomenon. Only soap operas can match it for longevity and popularity. So what's the secret to the Doctor's appeal?