• Whatever his true age, the Doctor still considers himself to be over 2,000 years old. Having two hearts gives him really high blood pressure. He always wins at chess and once met an emperor made of algae who fancied him.
• The Erehwon colony on Gliese 581 D is 20 light years from Earth. The city is a vast extension of the United Earth Colonisation Team space cruiser Erehwon, designated UESC 190484, which has systems designed to respond to a human presence and reanimate the cryogenically frozen colonists.