Judoon

The Judoon are a sentient alien species from Doctor Who. Often employed by various galactic powers as mercenary police, they carry out their contracts with rigid and ruthless efficiency and seem to care little about any innocents that happen to get in the way.

Biology
Judoon are humanoid beings that strongly resemble the Earth rhinoceros. Typically standing at 2 metres tall, they possessed great physical strength and endurance. The Judoon brain is small, capable of fitting within a human palm. Judoon have yellow blood and have extraordinary lung capacity that can hold large reserves of oxygen, allowing them to survive in low-atmosphere environments for extended periods of time.

Culture
The Judoon were known for their strict obedience to the law and their brutal efforts in maintaining it. Crimes like physical assault towards a Judoon incurred the death penalty, without chance for trial. The Doctor described them as logical, but stupid, and they seemed to favour methodical patterns of behaviour to a fault. Even on crucial missions, Judoons would obey local traffic laws, "Authorised personnel only" and "Pay and Display" signs, follow mission procedure rigidly and always got a form signed when commandeering transport. The Judoon were trained to use all known forms of transit, albeit not very well in the case of cars.

Their language was composed of many one-syllable words ending in a vowel, generally an "o" sound (such as "blo mo co jo") but occasionally an "a". Each sentence was composed of several of these words strung together. Despite the TARDIS containing a telepathic translator that turns all alien language into English, the Judoon language does not seem to be translated, even with both the TARDIS and the Doctor present in their company.

Although they did not laugh, Judoons would shake and make laughter-like noise when amused.

A favourite sport among the Judoon was nukeball, but it was illegal on their planet to avoid the destruction of the population. Judoon did not like opera.