Spoilers, sweeties.
The original title sequence from 1963 kicked off the episode.
BBC One
Totter's Lane, where the First Doctor parked his TARDIS while his grand-daughter Susan Foreman was at school, got a lovely wink at the opening of the episode.
Via BBC One
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 to be 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.
BBC One / Via who-lligan.tumblr.com
And we got a lovely little homage to TARDISes past via "the round things".
BBC One / Via ricktimus.tumblr.com
