Theory:Doctor Who television discontinuity and plot holes/City of Death


 * It's very unlikely a Human could withstand the earth's atmosphere 400 million years ago, yet Duggan, the Doctor or Romana do have a problem standing outside at that time.
 * Duggan, maybe, but the Doctor and Romana being Time Lords likely could. Another possibility is that the TARDIS was protecting them as well.


 * How does the Doctor twice manage to direct the TARDIS to a specific point when the randomiser is installed?
 * The sentience of the TARDIS has been long established, too, so it might have known to bypass the randomizer.


 * If the Countess has managed to go her entire married life without discovering that her husband is really a cycloptic, green-tentacled alien then either his skin suit is incredibly sophisticated to hold up to such intimate scrutiny, or their marriage is unconsummated.
 * Both are possibilities. It was only ever a marriage of convenience, and some aliens [including the Slitheen] have been seen to possess the ability to use "fully functional" human bodies as disguises.