1. The original title sequence from 1963 kicked off the episode.
2. Totter’s Lane, where the First Doctor parked his TARDIS while his granddaughter Susan Foreman was at school, got a lovely wink at the opening of the episode.
3. And here’s Coal Hill School itself, where companions Ian Chesterton and Barbara Wright taught. Look closely…
Chairman of the Governors: Ian Chesterton!
And right under that it reads “W. Coburn”, which is probably a nod to Anthony Coburn, who helped developed Doctor Who back in the ’50s and is believed to be behind the idea that the outside of the TARDIS should look like a police box.
4. And we got a lovely little homage to TARDISes past via “the round things.”
6. Speaking of TARDIS redecoration…
This line originally appeared during the Second Doctor’s run in regards to U.N.I.T. headquarters, then again in “The Three Doctors” special, and once more during Eleven’s run. The Doctor never does change, does he?
7. A machine that goes “ding” was back.
8. These Queen Elizabeth gags were finally explained! Doctor, you naughty boy.
No wonder she wanted your head in The Shakespeare Code.
9. The Doctor’s phone number has stayed the same since Season 4’s “Stolen Earth,” at least.
10. Ten’s last words broke our hearts a little bit all over again.
11. The Eleventh Doctor actually carves the date and time of the first-ever episode of Doctor Who into the tower’s wall.
It aired at 17:16 on 23/11/63.
12. And Clara drives past a clock displaying the time the first episode aired once more.
This time NOT in military.
13. Clara’s whiteboard at the start of the episode already had “no more” written on it.
“No more time…” to be precise.
WHAT DOES THAT TRAIL OFF INTO? Looks like maybe we were told exactly where this episode was headed from the start.
15. And these glasses sure do look familiar.
16. Kate’s not the only Lethbridge(-Stewart) who’s had to deal with multiple Doctors.
17. River’s shoes are apparently a weapon of mass destruction worth keeping in the Black Vaults.
Not that this is actually surprising, come to think of it. Via.
18. BUT! So is Amy’s pinwheel.
19. And then there’s a brief appearance of Torchwood’s magnetic clamps, as used in Doomsday.
20. Many of the Doctor’s faces and Companions are visible on Kate’s board.
21. Captain Jack, too, got a nod.
22. Arthur, the horse from Girl in the Fireplace, may have made an appearance.
24. The War Doctor’s regeneration was a direct echo of Hartnell’s final lines.
25. Bummed you didn’t get to see Hurt regenerate into Eccleston? Fans believe if you look closely at Hurt’s right eye in this scene, it actually does morph into Eccleston’s.
When the flames start to cover his eye, watch the eyebrow. Something definitely shifts.
26. The time line of this episode ties in wonderfully to season one’s whole “Bad Wolf” arc.
27. Tom Baker’s surprise cameo as “The Curator” basically broke the fandom.
28. As if we weren’t already done in by Capaldi’s eyes alone.
29. Speaking of, Capaldi is starting to make a wonderful amount of sense…
30. And if you watched The Five(ish) Doctors Reboot (which you should), you may recognize the shrouded Zygons as none other than a few of the other classic Doctors.
Maybe. It’s not been confirmed, but it’s fun to think that may be a vaguely disgruntled Peter Davidson under there. Via.