This weekend brought a rather fantastic surprise for fans of the venerable sci-fi series Doctor Who. The BBC announced yesterday that David Tennant, the tenth Doctor, and Billie Piper, who played his companion on and off during his run on the show, are both set to return for the series's 50th anniversary special. The two actors will join the current doctor, Matt Smith, and his companion, played by Jenna-Louise Coleman, for the episode, which will also co-star actor John Hurt. The special, which will begin filming next week and air later this year, will be written by show's executive producer and main writer, Steven Moffat. Tennant, who played the character for five years, last portrayed the Time Lord at the very beginning of 2010, an episode that Piper also appeared in.