Fridge / Doctor Who S36 E9 "Empress of Mars"

• When the Doctor first meets with Bill in his office, he tells her the reason he noticed her is that when she doesn't understand something, where most people frown, she smiles. When the Doctor sees the writing on Mars, he smiles.
• If the Victorian soldiers hadn't joined the Ice Warriors, if they had instead gone back home to Earth, they would have brought certain knowledge that there are other civilizations out there, and at least one nearby planet with gold, gems, and abandoned technology they could exploit and reverse-engineer. Space flight might have gotten a huge headstart!