* HeyItsThatGuy: [[Series/TheThickOfIt Malcolm Tucker.]] It's actually a little jarring, because while both characters are government workers, Frobisher is rather quiet and meek, compared to Tucker's assertive, angry nature.
** The actor also plays the father of the Roman family in the DoctorWho episode "The Fires of Pompeii" and would go on to play the Twelfth Doctor.
* WhatCouldHaveBeen: Martha Jones and Mickey Smith were supposed to appear in ''Children of Earth'', but Creator/FreemaAgyeman was [[Series/LawAndOrderUK busy]]. The two are [[WrittenInAbsence explained away as being on their honeymoon]] (though we don't know it's them married until ''Doctor Who'''s ''The End of Time'') and unable to help the team.