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Updated February 2015

A Zygon. Big, red rubbery thing covered in suckers. Surprisingly good kissers.

The Zygons were one of the several monster races which appeared in the BBC's longest-running and most popular sci-fi series, Doctor Who (1963-1989, 2005+). They only featured in one story in the original run and have only had one real appearance to date in the 21st Century, however as that appearance was in the show's 50th Anniversary it proves their status as a unique and very memorable creation.

Who Were the Zygons?

Short, squat, slightly bulbous humanoids that resembled a human foetus covered in suckers, the Zygons came from a distant planet, the name of which was never revealed. They had bright reddish-orange reptilian skin with mushroom-shaped suckers running across the main parts of their bodies, such as the head, shoulders, limbs and chest.

They seem to be an extremely long-lived race, with Broton and his five companions appearing to have stayed on Earth awaiting rescue from the 11th Century until the late 20th. They are also known to be mammalian and require a diet of lactic fluid, which they milk from giant sea serpents they call Skarasen.

Although according to the Tenth Doctor Zygons are surprisingly good kissers, Zygons have poison sacs in their tongues so they should be kissed with caution. How the Doctor has learnt about the Zygons' kissing ability and poisonous tongue sacs, which he mentions before being kissed by a Zygon disguised as Queen Elizabeth, is unknown. The Zygons can also emit a high-voltage electrical charge in their fingertips; when discharged, this can stun or kill.

The presence of Zygons can be detected by a machine invented by the Doctor that goes 'Ding!', although this was unable to pinpoint the Zygons' location.

Home World

When The Doctor first encountered the Zygons, Warlord Broton revealed that his home planet had been destroyed in what he believed to have been caused by a natural stellar explosion. It was later revealed that the explosion had been caused by the Time War, the conflict between the Time Lords and Daleks that threatened to burn the entire universe. Now exiled, the Zygons realised they needed to find a new home world. Although the Zygons had assembled their survivors in a refugee fleet, this would need centuries to make the journey to a new planet. The time taken would enable an advance party, such as Broton and his six companions, to terraform the Earth into a planet similar to their lost home and more suitable for colonisation. This would be done by using human slave labour and Zygon technology to raise the Earth's temperature, melt the Polar icecaps, create more lakes and ensure these have the correct mineral element contents.

A second group of Zygons also wished to conquer the Earth. Arriving in the 16th Century they hid in suspended animation inside paintings, waiting for human technology to become more advanced and living standards not so primitive before they were prepared to conquer the Earth. In the 21st Century they emerged, disguised themselves as members of UNIT¹, the Zygons infiltrated UNIT's Black Archive. This contained advanced alien technology that the Zygons intended to use to conquer the Earth. They were halted when the real UNIT personnel threatened to detonate a nuclear bomb buried beneath the Tower to stop them. With the Doctor's assistance, a fair treaty between humans and Zygons was reached, although the audience never learns what this involved.

Although a few Zygons have been defeated, what of the other Zygon craft cruising the galaxy?

Zygon Technology

The Zygons rely on organic technology (as they were highly organic creatures themselves) and their distinctive spacecraft was controlled by nodules instead of switches or levers, with thick leathery tissue for walls and muscular tendrils where cables might have been on other craft, reflected their organic technology. Despite the spacecraft's organic interior, the exterior appears angular with predominantly flat, metallic surfaces.

Although they have interplanetary travel, they do not seem to be as advanced a spacefaring race as others the Doctor encounters. For example, Broton, Warlord of the Zygons, was prepared to wait centuries for rescue when his craft was damaged, suggesting that the Zygons' rescue ships are rather slow. It also implies that they are not particularly easy to repair away from a dedicated workshop. As races such as the Cybermen, Daleks and Sontarans etc are able to travel wherever they wish in much shorter time periods, the Zygons' ships' propulsion system, called 'dynacron thrust', must therefore be much slower. This might be why the Zygons have not established any colonies prior to the destruction of their home world. That said, Zygon vessels are watertight and can successfully stay submerged for centuries.

The Zygons do not appear to have time travel capabilities, which may explain why they were early victims in the Time War. In 'The Day of the Doctor' they utilise stolen Time Lord art² as a means of suspended animation, implying that they cannot time travel into the future. The Zygons' aim then is to wait until human technology has advanced sufficiently to make their conquest of the Earth worthwhile, yet curiously they do not recognise the Doctor's TARDIS as being advanced technology. The Zygon leader had been inside the TARDIS while disguised as a horse, and his force make no effort to capture it. They prefer to impersonate Queen Elizabeth I in a plot that involves them being stranded inside paintings for centuries instead.

However, as soon as they emerge from stasis inside these paintings, one of their priorities is to gain access to time travel. When disguised as Kate Stewart, the Zygons plan to capture Captain Jack Harkness' vortex manipulator, which Clara keeps from their hands.

Shapeshifing: Let Zygons be Zygons

The Zygons themselves are imbued with biomorphic or shape-shifting abilities and can re-arrange their body molecules into an exact physical and vocal replica of any desired creature or individual. In 'Terror of the Zygons', the subject to be copied had to stand in a booth on board their craft for a DNA sample known as a 'body print' to be collected and transferred to the selected Zygon. Once in the form of the subject, the Zygons could move about undetected and gain the confidence of anyone. However, the sample would only last for a short while, meaning the Zygons had to return to their craft for a fresh sample.

In 'Day of the Doctor' it is revealed that Zygons can make copies of their subjects even if they are not kept in a booth. For instance, Zygons impersonate both Osgood and Queen Elizabeth I without either of them being captured. One also disguised itself as Kate Stewart, however this took place after it assaulted her, although she is merely stuck to a wall with gooey tentacles rather than kept in a body print booth. The Zygon commander also successfully impersonates a horse, although sadly we never learn whether or not the Zygons managed to fit a real horse into a booth inside one of their spaceships.

There seems to be a bond between the Zygon in disguise and the original subject they have copied. If they do not keep using the body print of those they are disguised as every few hours, the original subject dies. If the host dies, the Zygons cannot disguise themselves as that person ever again. Similarly, if a Zygon copy is killed, then the human being the Zygon is copying is released from the trance they are kept under inside their body print booths. The Zygon's dead body is completely destroyed, in a process known as dispersal, to keep the Zygons' presence secret.

The extent to which the Zygons become the subject they are disguised as is also unclear. The Zygon disguised as Osgood not merely looks exactly like Osgood, but even shares Osgood's memories. Although Zygons themselves are tremendously physically strong, when in disguise, they share the host's weaknesses. The Zygon-Osgood suffers from asthma because Osgood does. Similarly, the Zygon Commander is killed by Elizabeth because, in her words,

I may have the body of a weak and feeble woman, but at the time, so did the Zygon.

If a Zygon-in-disguise has its memory wiped, the Zygon is curiously unable to tell whether it is really a human or a Zygon. Does that mean that the hosts' memories and knowledge can predominate? When the Zygons first encountered time travel technology, namely the Doctor's TARDIS, one was disguised as a horse. Did a horse's natural thoughts about the TARDIS, such as the notable lack of grass and hay, prevent the Zygon impersonating it from noticing that it was in a time machine? Later a Zygon disguises itself as Kate Stewart, head of UNIT. This is when the Zygons become interested in time travel technology. If the Zygon-Stewart knows everything that Kate Stewart knows, is it Stewart's knowledge that sets the Zygon's course of action?

Perhaps the Zygons' most successful disguises are seen when they are able to hide in the Under Gallery, one of Britain's most secure vaults, by putting sheets over their heads. Their secret passage to their spaceship that requires them to use a stepladder to open is also particularly noteworthy.

Nessie the Skarasen

The original group of Zygons to come to Earth had stored in their ship an embryo of an amphibious 'sea serpent' called the Skarasen. The Skarasen produced lactic fluid that the Zygons required to survive. Reared and kept in a loch, it was occasionally spotted by humans - who called it the Loch Ness Monster. It was revealed that Broton had converted into an armoured cyborg, incapable of being hurt, even by nuclear weapons. Broton was able to control the Zygon using a device called a trilanic activator. He planned to use the Skarasen as the ultimate weapon to conquer mankind and enslave the world, although the Doctor was later able to free it, allowing it to return to the loch.

The Zygons' Creator

The Zygons were created by writer Robert Banks Stewart for the opening story of the show's 13th season. The Zygons were included in his story about the Loch Ness Monster as a means of providing an explanation for the mythical Monster's existence. Robert Banks Stewart was himself a Scot who wrote just one other story for the series, 'The Seeds of Doom' (1976). In the early 1980s, he created the popular detective series Bergerac, which ran for over ten years and featured Louise Jameson, who played the Fourth Doctor's companion Leela from 1977 to 1978.

Story Guide

Below is a description of the Doctor Who stories that feature the Zygons.

'Terror of the Zygons' (1975)

A small group of Zygons stranded on Earth discover their home planet has been destroyed. Commanded by a Zygon warlord called Broton in Loch Ness, Scotland, they seize the opportunity to take the forms of several of the locals of the nearby village of Tullock, including the Duke of Forgill. Broton plans to conquer Earth for the survivors of the Zygon race to colonise.

Broton commands the Skarasen to destroy oilrigs off the Scottish coast as a trial of strength. When the Fourth Doctor, assisted by Sarah Jane Smith, Harry Sullivan and the forces of UNIT under Brigadier Lethbridge-Stewart, investigate, the Zygons are uncovered as having a hidden spaceship, accessible through the Duke of Forgill's castle's cellar.

The Zygons have taken the forms of several of the locals of the nearby village of Tullock as cover for their activities. Broton disguises himself as the man in charge of the region, the Duke of Forgill. Aided by these disguises, they capture the Doctor and pilot their spaceship to hide in a quarry near London.

The Doctor, imprisoned aboard the craft, escapes and frees the captive humans whom the Zygons had impersonated. He then causes the Zygon's craft to self-destruct, and all the Zygons except Broton are destroyed in the resulting explosion. Broton, wearing the Duke of Forgill's form, attends a World Energy Conference in London, which he plans to destroy by controlling the Skarasen, which is swimming up the Thames.

Can the Doctor track Broton down? Will Broton condemn humanity to be eliminated by the Skarasen? Will the world be destroyed by the beast of Loch Ness?

The four 25-minute episodes were written by Robert Banks Stewart and directed by Douglas Camfield.

'The Power of Three' (2012)

In a minor scene, the Eleventh Doctor decides to treat Amy and Rory to a trip in the Savoy Hotel in 1890 as an anniversary present. However it is later stated that the hotel was on top of a Zygon base and the staff were Zygon impersonators...

Although the Zygons are mentioned, the audience does not see them. The 45-minute episode was written by Chris Chibnall and directed by Douglas Mackinnon.

'The Day of the Doctor' (2013)

The Tenth Doctor is out wooing Queen Elizabeth in 1562 when he discovers a Zygon impersonating her and is unable to tell the real and imposter apart. Meanwhile in the 21st Century, the Eleventh Doctor has been brought to the National Gallery's secret Under Gallery by UNIT forces commanded by Kate Stewart, the Brigadier's daughter. There he encounters a time portal that sends him back to Elizabethan England. In Tudor times the Tenth, Eleventh and War Doctors unite and investigate the Zygons' plan, which is to use Time Lord art as a means of staying in suspended animation, allowing them to invade in the future when mankind has developed to a more technologically-advanced species.

The Zygons emerge from hiding and impersonate members of UNIT, including Stewart and her asthmatic scientific advisor, Osgood. To prevent the subjugation of Earth, the real Stewart plans to detonate a nuclear warhead that would destroy the Zygons, as well as kill everyone in London. Will the three Doctors return to the 21st Century before the bomb's warhead reaches zero?

Written by Steven Moffat, directed by Nick Hurran, this 76-minute long episode was broadcast on 23 November 2013, Doctor Who's 50th Anniversary. 'The Day of the Doctor' was not only shown on television, where it was the UK's most watched drama of 2013, but also shown in over 1,500 cinemas worldwide, 834 cinemas showing it in 3D, 440 in the UK alone. Broadcast in 94 countries across 6 continents, dubbed and subtitled into 15 different languages, the Guinness Book of Records confirmed this episode is the largest ever simulcast of a television drama.