Steven Moffat is nervous about writing the 'Doctor Who' 50th anniversary episode.
The sci-fi show's chief writer feels ''tremendous pressure'' not to let fans of the long-running BBC One programme down by penning one of the best adventures the Time Lord has ever been on for the hotly-anticipated special episode.
He told The Sun newspaper: ''I'm writing the 50th anniversary episode right now and it's half exciting and it's half absolutely terrifying. I feel tremendous pressure not to let people down. So that's very hard.
''You can't please everybody all the time and it's a mistake in a way to try. But you don't want anybody to feel let down by a big anniversary episode.''
Speculation about which beloved characters will return for the one-off episode, 'Doctor Who: The Light At The End', alongside Matt Smith has been rife for months.
While Billie Piper, who played the Doctor's companion Rose Tyler from 2005 to 2006 before her final appearance in 2010, has ruled out a return, David Tennant - who played the Time Lord from 2005 to 2010 - looks likely to come back after coyly responding to a question about it with a wink.
John Barrowman is also desperate for his alter-ego Captain Jack Harkness to make a comeback and recently hinted: ''I haven't been asked. I would love to if they ask me.''
'Doctor Who: The Light At The End' will air in November.
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