Raxacoricofallapatorian

The Raxacoricofallapatorians are a race of large, calcium-based aliens from the planet Raxacoricofallapatorius, who have faced off with the Ninth Doctor several times.

Appearance and Biology
Raxacoricofallapatorians are large, bulky humanoid that are around 3 metres tall. Despite their large bulk, they are capable to suprising speeds and can easily overpower a human. They have baby-like faces with large black eyes with sideways blinking eyelids. They have long arms with three sharp claws which they use to kill their prey. They 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, allowing them to go without food for longer. (DW: The Monsters Inside) Raxacoricofallapatorians are predators by nature and can hunt by scent.

Due to their calcium-based nature, Raxacoricofallapatorians are vulnerable to acetic acid and react explosively with it. (DW: Aliens of London)

Technology
The Raxacoricofallapatorians are more advanced then humans, and have developed space travel by 2006. They could also modify a pig into a humanoid using their own technology. (DW: Aliens of London)

The Raxacoricofallapatorians’ most distinguishable technology is their compression field. The criminal Slitheen 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). Despite this, the Slitheen still needed to use larger humans, since the compression fields have limited power. (DW: Aliens of London, World War Three)

Culture
The Raxacoricofallapatorians still have the death sentence for dangerous criminals like the Slitheen family, 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)