Welcome to this week's Doctor Who's Day roundup, a deep dive into the most fannish corners of social media and the internet, looking for nuggets of astonishment. And this week, we begin with "Empress of Mars," an adventure that reunites the Doctor with an old friend and an even older foe.

Let's start with introductions. First, from writer Mark Gatiss:

https://www.youtube.com/watch?v=kth1ng49-O8

• And add some thoughts from Steven Moffat too:

https://www.youtube.com/watch?v=KDTXNsxnNR0

• Mark had this to say about the Ice Warriors:

https://www.youtube.com/watch?v=QRrI05T9b3Y

• And Third Doctor fans got to see the hermaphrodite hexapod Alpha Centauri make a comeback:

https://www.youtube.com/watch?v=s1KF12TG8OE

https://twitter.com/RadioTimes/status/874369215653752832

• And there is fan art:

https://twitter.com/beatdropsout/status/873974553646706688

http://owenoak95.tumblr.com/post/161726431263/doctor-who-9-empress-of-mars-tools-used

https://twitter.com/JeffGrampus76/status/873892177339977729

https://twitter.com/HSIAImbecile/status/873223029001682944

https://twitter.com/bmax67/status/873207599981899777

http://joscribbles.tumblr.com/post/160886224818/i-am-100-here-for-supportive-grandadtwelve

http://julielilac.tumblr.com/post/161737883612

https://twitter.com/jaseskywalker/status/873197488894869508

https://twitter.com/BethanAppleArt/status/872375145968652288

• Let's take a closer look:

https://www.youtube.com/watch?v=C0rEa1n7Iek

• Mark also appeared with Matt Lucas on Doctor Who: The Fan Show:

https://www.youtube.com/watch?v=VG1iTe1tniw

• And look! Fact files:

https://twitter.com/bbcdoctorwho/status/873618310058954754

https://twitter.com/anglophenia/status/874373033586302976

• And backstage shots:

https://twitter.com/DoctorWho_BBCA/status/874352355377946624

• There's a chat with the dastardly Catchlove, played by Ferdinand Kingsley:

https://www.youtube.com/watch?v=d6cfGPHiX6M

• And a quiz:

https://twitter.com/bbcdoctorwho/status/873951336882221057

• And this is just... whoah:

https://twitter.com/claytonhickman/status/873706995756539904

Here's what else has been going on in space and time this week:

• A Dalek-led examination of what Doctor Who would look like if other actors had been cast as the First or Second Doctors:

https://www.youtube.com/watch?v=QctIQ_EDroI

• Useful info:

https://twitter.com/AnOldLefty/status/874378877065453568

• Michelle Gomez on Missy's TARDIS:

https://www.youtube.com/watch?v=GC-A_33Y8NA

• Digital Doctors:

https://twitter.com/Horsenburger/status/874366192298991616

• Help the Doctor on Skype:

https://twitter.com/bbcdoctorwho/status/871781964508008449

• Birth of the Angels:

https://twitter.com/BBCRadio4/status/873137535777681408

• Donna Noble in cartoon form:

https://twitter.com/joserb93/status/873423665039364097

• A fan trailer for the Third Doctor alternate reality epic "Inferno:"

https://www.youtube.com/watch?v=bRvzq_u8ksc

• Speaking of whom:

https://twitter.com/shaneoid77/status/873735077456379904

• Bill fan art, one year on:

https://twitter.com/billiamquilliam/status/874375074853400576

• And finally, let's prepare for this week's dark tale, "The Eaters of Light:"

https://www.youtube.com/watch?v=0mcPh5rKHbc

https://www.youtube.com/watch?v=UlwvGVPY2wk

TTFN!