- The return of the Mondasian Cybermen: Admittedly, we've seen plenty of cybermen in recent years, but I love a good throwback - and seeing the original cybermen excited me nearly as much as when the Autons appeared in the ninth Doctor's first episode!
- Bill Potts clinging to her humanity: The scenes where Bill refused to accept that she'd been made into a cyberman were simply gut-wrenching! I have throughly enjoyed getting to know the Doctor's newest companion this season, and I wish her story hadn't ended so soon - but honestly, the ending was somewhat ambiguous, so who knows?
- The Master and Missy: Although the return of John Simm as The Master had been hinted at online, the intriguing chemistry between him and Michelle Gomez's Missy was fantastic!
- Companion flashbacks: We all know the Doctor doesn't like to regenerate, but seeing his memories of all the companions of recent years (plus one older flashback) gave me goosebumps!
- The end...or is it? Peter Capaldi has announced he's leaving, and the 12th Doctor has begun showing signs of regeneration - but clearly he's not done yet, and the Christmas episode promises to bring not only the introduction to the as-yet-unknown 13th Doctor, but also a visit from the first - played by David Bradley, who first portrayed William Hartnell in the BBC's An Adventure Through Space and Time.
The only question that remains is - how are we supposed to wait nearly six months for the Christmas episode?!