Raxacoricofallapatorian

The Raxacoricofallapatorians are a race of large aliens from the planet Raxacoricofallapatorius. The Doctor has faced off with certain criminal families of the Raxacoricofallapatorian species, namely the Slitheen and Blathereen families.

Biology
Raxacoricofallapatorians are large, bulky humanoids that are around 3 metres tall. They have thick, lumpy skin, ranging in colour from a yellowish green to a paler, grey-green. (NDA: The Monsters Inside) They have the instincts of a hunter and long arms with three sharp claws which they use to kill their prey. Despite their large bulk, they are also capable of surprising speeds and can easily overpower a Human. Raxacoricofallapatorians can hunt by scent and can identify species and emotional state by smell. They can also sense the pain of closely related individuals from far away. (DW: Aliens of London, World War Three)


 * This ability to sense the pain of other individuals may be telepathy, since it was shown to work from across planets. (NDA: The Monsters Inside)

Raxacoricofallapatorians hatch from large green eggs with several tendrils. The females of the species can create poison when in danger, which can be released by a dart-like claw or by their breath. (DW: Boom Town) Raxacoricofallapatorians have a more efficient metabolism then a Human, meaning they eat every few weeks and produce less waste. Raxacoricofallapatorian blood is red and their tears are milky in colour and slightly acidic. (NDA: The Monsters Inside) Due to their calcium-based biochemistry, Raxacoricofallapatorians are vulnerable to acetic acid and react explosively with it. (DW: Aliens of London)


 * Humans and most near-humans have a carbon-based biochemistry.

While all members of this species to appear belong to dangerous families, the species it's self does not seem to be inherently cruel or evil, as the Doctor gave Blon a second chance by putting her egg with a decent family.



Technology
The Raxacoricofallapatorians are more advanced then humans and had developed faster-than-light travel in the form of slipstream engines sometime prior to 2006. They could also modify a pig into a humanoid form using their own technology. (DW: Aliens of London) Some of the Raxacoricofallapatorian technology looks organic in nature. While in Justicia, Ecktosa and Dram used sticky nets as hammocks. This nettings were covered in a slime that quickly harden away from body heat. Other Raxacoricofallapatorian buildings had their floors covered in a sticky substance. (NDA: The Monsters Inside)

The Raxacoricofallapatorians’ most distinguishable technology is their compression field. The Slitheen and Blathereen are able to disguise themselves as other, smaller humanoids by fitting into their skins. This is done with the compression-field collars that they wear on their necks. Their size is controlled by the movement of gas, which causes a condition like flatulence, but with a rotten tooth smell (due to their calcium-based biology). (DW: Aliens of London, World War Three) These individuals originally needed to be large, but the advancement of technology meant smaller skins could be used. (NDA: The Monsters Inside)

Culture
The Raxacoricofallapatorians still have the death sentence for dangerous criminals like the Slitheens, which is carried out in a gruesome way. The criminal is lowered into a cauldron of acetic acid, which is then heated to boiling. The acidity of the solution is formulated to dissolve the skin, allowing the internal organs to drop into the liquid while the condemned is still alive, resulting in a slow and painful death. (DW: Boom Town)

Based on the comments of Blon, Raxacoricofallapatorians neither brush their teeth or prepare their food in complicated ways. (DW: Boom Town)

Two known Raxacoricofallapatorians insults are "May plaque brown your belly" and "May your mother boil in the cauldron of atonement". Both are presumably related to their calcium based biology. (NDA: The Monsters Inside)

Minor references

 * The severed arm of a Raxacoricofallapatorian found its way into Henry van Statten's private museum of alien artefacts. (DW: Dalek)


 * The arm may have come from off the body of a dead member of the family Slitheen.


 * While attempting to bluff the Sycorax leader out of attacking Earth, Rose namedropped the Raxacoricofallapatorians. (DW: The Christmas Invasion)


 * Rose Tyler remarks the Abzorbaloff as "a bit Slitheen", but when the Doctor asks the Abzorbaloff reveals it is from Clom, Raxacoricofallapatorius's twin planet. The Abzorbaloff spoke of the Raxacoricofallapatorians with contempt. (DW: Love & Monsters)