Doctor Who: 14 Cool Details Revealed In Steven Moffat's Eleventh Hour Commentary
4. Moffat Wrote (And Then Cut) A Scene That Explained Why Prisoner Zero Was In Jail
As the name implies, Prisoner Zero - the episode's shape-shifting villain - is a prisoner. He/she/it escapes from jail through a crack in Amelia's bedroom wall, hides in her house, and proceeds to wreak havoc throughout the peaceful village of Leadworth.
However, we never learn why Prisoner Zero was put in jail in the first place, and that's because Moffat cut the explanation from his script.
During the commentary - when asked about Prisoner Zero's original crime - Moffat states that it was something to do with invading another planet by "impersonating an army", but he quickly got rid of this idea at the scripting stage, because he thought "no-one would care".
And honestly... he was right! You don't tend to hear many Who fans complaining about the lack of a Prisoner Zero backstory, after all.