Two planets missing, two Rose references ("She's coming back") and the second mention of the Medusa Cascade (which was mentioned by the Master last year). Not sure of the Agatha Christie reference so far this week though.
Excellent episode yet again - lovely humour, gripping storyline and involving characters.
"I'm Spartacus." "So am I." *snerk*
TK Maxximus. *double snerk*
Fascinating to see how the Doctor sees the timeline : fixed points and flux points - only the one kind can be changed. I imagine it's like a river flowing along a route; minor detours like someone living instead of dying can be like a rock in the flow, and the river just resumes its normal course. However, something like Pompeii would be equivilent to a major diversion down a different watershed.
And more looking at how the translation circuit works again. Words in the actual language you're speaking get translated back to English apparently. Intriguing.