The BBC Official Doctor Who Twitter account confirmed today that the 50th Anniversary special would see the return of the classic Doctor Who foe, the Zygons. But just who are the Zygons? Here's a brief introduction to the aliens for those who may not have encountered them before.
The Zygons were an alien race encountered by the Fourth Doctor along with Sarah Jane Smith and Harry Sullivan in the 1975 serial Terror Of The Zygons. Having crash landed on Earth centuries ago, they remained in hiding under Loch Ness, plotting to take over the Earth after learning that their own planet Zygor had been destroyed. The Zygons also controlled a huge Cyborg, the Skarasen, which was their food source, and was recognised by many as the mythical Loch Ness Monster. Attacks by the Skarasen on oil rigs had alerted UNIT to the presence of the alien threat.
Zygons are humanoid in shape but hideously ugly, with stocky bodies and huge cone shaped heads with small, inset facial features. Their bodies are orange-brown in colour, leathery and covered in suckers.The Zygons are able to shape shift, often taking the bodies of significant and powerful people whose bodies they hold on their ship in suspended animation in order to maintain the link with the original body form. Zygon technology tends to be quite organic in nature.
David Tennant has previously said that the Zygons were his all-time favourite Doctor Who alien.