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Doctor Who race
A child member of the Slitheen family as seen in Revenge of the Slitheen (2007).
First appearance"Aliens of London" (2005)
In-universe information
Home worldRaxacoricofallapatorius
TypeLiving calcium bipeds
AffiliationVarious (families)
Slitheen, as shown at the Doctor Who Experience.

The Slitheen are a fictional family of Raxacoricofallapatorians, massive, bipedal extraterrestrials, from the British science fiction television series Doctor Who. They are adversaries of the Ninth Doctor and later Sarah Jane Smith. The Slitheen are a family of egg-laying calcium-based aliens from the fictional planet Raxacoricofallapatorius. Though their family name is Slitheen, their species is named Raxacoricofallapatorians. The Slitheen are instinctive hunters, who are trained from a young age to be ruthless criminals whose main motivation is profit. They were convicted in their home world and are not willing to return to their planet in fear of receiving a death sentence.

The Slitheen first appeared in the 2005 series episodes "Aliens of London" and "World War Three", and subsequently recur in later episodes of both Doctor Who and the spin-off series The Sarah Jane Adventures.

Physical characteristics

Adult Slitheen are 2.4 metres (8 ft) tall with overweight but muscular builds, long forearms, powerful sharp claws, and baby-like faces. They have pairs of eyelids, which move sideways and have a nictitating membrane. They possess immense physical strength, as they are shown to be strong enough to lift people off the ground. They have a highly developed sense of smell, as they are able to smell adrenaline, and hormones in people, and can sense if one of their own dies. Female Raxacoricofallapatorians can produce poisons within their bodies to use against their enemies. Known methods of delivery include a poisoned dart that is formed in their finger and then fired, and an exhalation of poisoned breath. Members of the Slitheen family have green skin, though there is variation in the skin tone of other Raxacoricofallapatorian families. In The Sarah Jane Adventures serial The Gift, members of the Slitheen-Blathereen family group are seen to have orange skin. The Slitheen also have hyphenated surnames, which allow The Doctor to deduce their planet of origin.

The Slitheen disguise themselves by crawling into the skins of their victims, using compression fields created by a collar worn around their necks to squeeze their huge size into a smaller space. Initially, the compression ratio was limited, so the disguises tended to be obese people, though some disguises are also slim people. This issue was overcome by new technology by the time of The Lost Boy, in which the skins of thinner people were used. By the time of "From Raxacoricofallapatorius with Love", shorter people could also be used. The exchange of gases that compression entails also builds up within the acquired skin, causing very loud flatulence in humans (the expelled gas smells like bad breath, which the Doctor noted was a form of calcium decay—though, in reality, bacteria that causes tooth decay is different from those that cause bad breath). This side-effect is also overcome by the newer technology in The Lost Boy.

Gas exchange

When the Slitheen are in their skin suits, they break wind loudly; they call this the gas exchange. This can also be caused by over-eating. In The Gift, Sarah Jane and the gang destroy their source of food, a plant called Rackweed, which is native to Raxacoricofallapatorius. The Rackweed, when digested, is in their stomachs. Using the audio of every audio-producing device in the vicinity, Mr. Smith triggers a sound in the attic. This causes the Slitheen-Blathereen aliens to start farting uncontrollably, and through the subsequent vibration of the sound and their own farts, their stomachs explode. Clyde then says the Blathereen aliens had "farted themselves to death."


Raxacoricofallapatorians are vulnerable to acetic acid, which reacts explosively—and fatally—with their bodies, making Slitheen allergic to vinegar, ketchup and Coca-Cola. One Raxacoricofallapatorian method of execution involves lowering the condemned into a cauldron of acetic acid, heated to boiling. The acidity dissolves the skin, causing the internal organs to drop into the liquid while the condemned is still alive, reducing them to "soup" in a slow and painful death. In "World War Three," when a single Slitheen was electrocuted, the effects were transmitted to other Slitheen, even those across the city.


Writer and showrunner Russell T Davies based the idea of a family of antagonists around the Aubertides from the Virgin New Adventures novel "Human Nature."[1] The decision to have the Slitheen invade Downing Street was inspired by the Girls Aloud "Jump" music video.[2] In pre-production of the episodes, it was decided for the Slitheen to appear both as physical costumes and as CGI models. However, it was later found that the costumes did not match their CGI counterparts, and the costumes were discovered to have many limitations, leading to the team electing to avoid a hybrid approach of costumes and CGI for future episodes.[3] Davies was impressed by Annette Badland's performance as Blon Fel-Fotch Pasameer-Day Slitheen during the production of "Aliens of London" and "World War Three," and asked her if she would be willing to return to the programme for the future. Seeking to revisit the character, he selected the eleventh episode of Series One to focus on it, which eventually became "Boom Town." As the costumes and CGI models already existed, very little strain was placed on the budget, allowing for a climactic finishing sequence in the episode.[4]

Davies initially pitched the idea of The Sarah Jane Adventures with the idea of "Sarah Jane versus the Slitheen." As the monsters held a particular appeal for younger viewers and were a part of the first series of Doctor Who's revival, it was felt that they were an ideal monster to include in the series, and they also established the connection with Doctor Who.[5]

In an early draft of "The Gift," the Slitheen had a bigger role, aiding the human characters in stopping the spread of "Yorrum Grass" (an earlier version of the "Rakweed" used in the final episode) before betraying them to the Blathereen. The Blathereen themselves were thought to be a cost-saving measure, as a simple repaint of the Slitheen costumes, but new costumes ended up being constructed for the Blathereen regardless.[6]


When they first appeared in "Aliens of London" (set in 2006), the Pasameer-Day branch of the Slitheen had been in Great Britain for some time, having infiltrated various levels of British society, from community leaders and military personnel to mid-level politicians and government officials. Their intent was to instigate World War III and sell the radioactive remains of Earth to a depressed galactic economy as fuel for interstellar spacecraft. They staged the crash landing of an alien spaceship in central London, setting up a cybernetically augmented pig as an "extraterrestrial" body.

A Slitheen, as it appears at the Doctor Who Experience

With the world in a state of heightened alert and panic, and with their commander Jocrassa assuming the role of Acting Prime Minister, they persuaded the United Nations to allow the United Kingdom to use its nuclear arsenal against the alien "massive weapons of destruction". Before the Slitheen could receive the launch codes, the Ninth Doctor arranged for a Harpoon missile to demolish 10 Downing Street, ending the scheme and killing all but one of them who managed to escape through an emergency teleport.[7]

Jocrassa's sister Blon Fel-Fotch Pasameer-Day Slitheen, who had assumed the identity of Margaret Blaine of MI5, survived and reappeared in the episode "Boom Town". In the intervening six months, "Blaine" was elected as Lord Mayor of Cardiff and planned to leave Earth by using the energy from a new nuclear power station to interact with the Cardiff Rift, unconcerned that the planet would be destroyed in the process. Blon was stopped by the Doctor and his companions, and on exposure to the "heart" of the TARDIS, regressed to an egg. The Doctor took the egg to the hatcheries on Raxacoricofallapatorius so she could be given a second chance at life and be raised by a peaceful Raxacoricofallapatorian family.[8]

Some years after the events of "World War Three", in Revenge of the Slitheen (set in either 2008 or 2009)[a] another group of Slitheen infiltrated a construction company with plans to turn off the Sun and destroy Earth by draining the world's energy to avenge the deaths of the Pasameer-Days. It is mentioned that the Judoon have begun to force out the Slitheen and that the various other Raxacoricofallapatorian families have been working against them. The families Blathereen and Hostrazeen are mentioned as part of the Raxacoricofallapatorian ruling bodies: the Senate and the Grand Council. After their Commander, Glune, was killed by Maria Jackson, Luke Smith was able to trick the Slitheen into resetting their machinery, which then malfunctioned and exploded. Two of the remaining Slitheen were killed, and the others escaped, including one of their children, Korst, the first child Slitheen to appear.[9]

The Slitheen returned in The Lost Boy where, using the newer compression technology, two Slitheen named Dax and Bloorm posed as Luke's 'real' parents Jay and Heidi Stafford. They were under the command of Korst, who planned to avenge the deaths of his family.[10] Another Slitheen (who was either a child or a short adult) appeared in the 2009 special "From Raxacoricofallapatorius with Love", masquerading as a galactic diplomat in an attempt to steal Sarah Jane's robot dog K-9.[11]

The Slitheen appeared in the New Series Adventures novel The Monsters Inside by Stephen Cole. When the Ninth Doctor and Rose are arrested in the Justicia System in the year 2501, the Doctor shares a cell with Dram Fel-Fotch and Ecktosca Fel-Fotch Happen-Bar Slitheen, who claim that after the Earth incident, the remnants of the family went bankrupt and had become historians. The Slitheen had not actually given up business and were in conflict with a more influential family, the Blathereen. When the Doctor and Rose defeat an attempted Blathereen takeover of the system, the Slitheen are pleased to see they can once again become the profit-holders of their race. The Blathereen were mentioned again in the Sarah Jane Adventures episode Revenge of the Slitheen.

In the Series 3 finale of The Sarah Jane Adventures, The Gift, a pair of Slitheen-Blathereen from an intermarried line of the two families attempted to overrun Earth with Rakweed, a plant native to Raxacoricofallapatorius and used as an addictive vegetable. Using sound waves, the Slitheen-Blathereen are blown up by the Rakweed in their stomachs.[12]

In "Dalek", a stuffed Raxacoricofallapatorian arm was among a collection of alien artefacts owned by American billionaire Henry van Statten in the year 2012. Rose later mentioned the Slitheen Parliament of Raxacoricofallapatorius in "The Christmas Invasion" (though her impromptu speech was a pastiche of phrases she had picked up on her travels with the Doctor). A member of the Slitheen was captured by the Graske in the mini-episode "Attack of the Graske," and later fought back against its capturer after being freed. Rose accused the Doctor (after his regeneration into the Tenth Doctor) of being a Slitheen in disguise in the 2005 Children in Need mini-episode and the Doctor makes a passing reference to the Slitheen and their skin-suits in "The Runaway Bride".

The Abzorbaloff, an alien from Raxicoricofallapatorious' twin planet Clom

In the 2006 series episode "Love & Monsters", an alien called the Abzorbaloff, whose natural form is similar to that of the Slitheen, claims to be from Raxacoricofallapatorius's twin planet Clom. The Slitheen spaceship from "Aliens of London" was also seen in a flashback in the same episode.

A Slitheen appears briefly in the Tenth Doctor novel The Nightmare of Black Island by Mike Tucker, created from Rose's memories, along with a Dalek and the Nestene Consciousness. The Slitheen are also briefly referenced by the Doctor in the same novel while speaking to a member of the Cynrog about hiding under human-like skinsuits. In the later novel, The Last Dodo, when the Doctor is asked if he has ever had a dream, he claims to have a recurring one in which a Slitheen on a rocking horse chases him. The Slitheen appear as a sketch in John Smith's "A Journal of Impossible Things" in the episode "Human Nature". The scribbled words by the drawing note that "it's always for money."

In the Torchwood episode "Reset", a newspaper clipping of Blon posing as Margaret Blaine, previously seen in "Boom Town", can be seen as Martha Jones enters the Hub.

The Doctor Who website" features a segment called Captain Jack's Monster Files, narrated by John Barrowman, which provides information about alien species. An episode focusing on the Slitheen [1] shows a family tree that refers to a number of related families, all with the suffix, -een, with the exception of the 'Absorbalovian Rebels', referring to the Absorbaloff from "Love & Monsters, from the twin planet of Clom.

The Slitheen are mentioned in the audiobook Wraith World, when Clyde Langer remarks he cannot understand why Luke and Rani would want to read about made up adventures when they have faced the Slitheen.

Though the Slitheen do not appear in "The Time of the Doctor", the Doctor mentions them as among the forces gathered around Trenzalore.

Doctor Who


The Sarah Jane Adventures




Other appearances


Writing for the Radio Times in a review of "Aliens of London," criticized the Slitheen, as well as the concept behind their compression fields, stating that "The Slitheen will never work for me. It speaks volumes that the costumes were often reused in the more child-oriented The Sarah Jane Adventures and have been left to rot since Steven Moffat took over Doctor Who."[13] Arnold T. Blumburg, writing for Now Playing, highlighted the Slitheen costumes as "nicely designed monsters," though criticized the usage of zippers on their in universe skin suits, as well as the childish humor surrounding the Slitheen.[14] Alasdair Wilkins, writing for The AV Club, defended the Slitheen's associated fart humor, but criticized how the two-parter doesn't "...take the Slitheen themselves seriously," citing his disappointment, "...because there’s plenty of intelligence in how the two-parter portrays the Slitheen."[15]

Marc DiPaolo, writing about political satire in Doctor Who, cited the Slitheen as an example of this, stating that "If one were to imagine that the American government was the one infiltrated by the Slitheen, that the World Trade Center was destroyed by a plane instead of Big Ben by a spaceship, and crude oil was the Slitheen’s goal instead of spaceship fuel, then the episode would play as an allegorized dramatization of the 9/11 conspiracy theory presented by Thierry Meyssan in the book L’Effroyable Imposture."[16] A physics paper for The University of Leicester calculated the force of the Slitheen's compression fields.[17]


  1. ^ It is stated in "Invasion of the Bane" that K-9 Mark IV has been in a black hole for 18 months, "School Reunion" having taken place in 2007.[citation needed]


  1. ^ Mcalpine, Fraser (2015). "'Doctor Who': 10 Things You May Not Know About 'Aliens of London'". BBC America. Retrieved 15 March 2020.
  2. ^ McEwan, Cameron (18 September 2017). "Former Doctor Who boss: Girls Aloud video was influence for Slitheen invasion". Doctor Who Tv. Retrieved 4 April 2020.
  3. ^ "Aliens Of London / World War Three | A Brief History Of Time (Travel)". Retrieved 21 July 2023.
  4. ^ "Boom Town | A Brief History Of Time (Travel)". Retrieved 21 July 2023.
  5. ^ "Revenge Of The Slitheen | A Brief History Of Time (Travel)". Retrieved 21 July 2023.
  6. ^ "The Gift | A Brief History Of Time (Travel)". Retrieved 21 July 2023.
  7. ^ "Aliens of London/World War Three"
  8. ^ "Boom Town"
  9. ^ "Revenge of the Slitheen"
  10. ^ "The Lost Boy"
  11. ^ "From Raxicoricofallapatorius with Love"
  12. ^ "The Gift"
  13. ^ "Aliens of London/World War Three ★★★". Radio Times. Retrieved 21 July 2023.
  14. ^ "Now Playing Magazine". 21 April 2005. Archived from the original on 21 April 2005. Retrieved 21 July 2023.
  15. ^ "Doctor Who: "Aliens Of London"/"World War Three"". The A.V. Club. 1 December 2013. Retrieved 21 July 2023.
  16. ^ DiPaolo, Marc, "Political Satire and British-American Relations in Five Decades of Doctor Who" (2010). Faculty Books & Book Chapters. 7.
  17. ^ Evershed, Mabel Elisabeth; Baldwin, Emily Jane; Beedle, Thomas James; Cook, Naomi Esther (18 November 2017). "P5_1 Squashing Slitheen". Physics Special Topics. 16 (1).