Ood

The Ood, also known as Oodkind, were a gestalt species of telepathic humanoids native to the Ood Sphere. Humanity enslaved the Ood, mutilating them to ensure a dedication to servitude.

Biology
The Ood were a humanoid species with coleoid tentacles used for feeding purposes located on the lower portions of their faces. They had no vocal cords and instead communicated by telepathy. The Ood had long lifespans; Ood Sigma lived 100 years after the human enslavement ended and the Tenth Doctor was surprised at this, thinking he should have been much older. (TV: The End of Time)

The Ood had two brains: a forebrain in the head and a secondary hindbrain. The hindbrain was usually held in their hands, and was connected by an umbilical cord-like connection to their faces. The forebrain did much of the thinking and stored the telepathic sensors. The hindbrain processed memory and emotions, leading to mental instabilities when removed. The Ood could survive with it being removed and replaced with the more commonly seen translation sphere that connected to an Ood's nervous system. (TV: Planet of the Ood) The Ood Elder had a larger, external forebrain. (TV: The End of Time)

Under normal circumstances the Ood were benign and harmless creatures. However, due to their brain structure they were susceptible to manipulation, as demonstrated by how easily the race was enslaved by Ood Operations. (TV: Planet of the Ood) More worryingly, their passive telepathy allowed them to be easily controlled and/or possessed by more powerful telepathic entities, such as the Beast (TV: The Impossible Planet) and House. (TV: The Doctor's Wife)

Telepathy and mental abilities
The Ood were originally a hive mind led by the Ood Brain, using their hindbrain to "sing" with each other. The colour of an Ood's eyes changed with the level of telepathic activity, normally glowing bright-red but turning to white when not connected to a hive mind. Humans, who only knew the Ood in their telepathy-disabled form, misinterpreted the presence of red eyes as a disease, known as "red-eye". (TV: Planet of the Ood) Under the control of House, one Ood's eyes glowed green. (TV: The Doctor's Wife)

History
The Ood were a peaceful herd-race originally. In the 39th century, humanity discovered the Ood, enslaved them, and used them to perform menial tasks throughout the three galaxies of the Second Great and Bountiful Human Empire. The external hindbrain of the Ood was extracted by Ood Operations and replaced with their translator globes. With their connection to the Ood Brain severed, they followed the orders of humans. Ood Operations kept this procedure a secret from the rest of humanity, spreading the belief that the Ood were naturally servile and offered themselves for servitude. (TV: Planet of the Ood)

By the 42nd century, it was claimed that every human had an Ood servant. They were generally barely even regarded as being alive, and were considered to be expendable. Despite this, an activist group, the Friends of the Ood lobbied for the cause of their freedom. (TV: The Impossible Planet)

In 43K2.1, the Ood were being used for menial labour on Sanctuary Base 6 on Krop Tor. The Ood knew of prophecies regarding the Beast which the Walker Expedition would later discover. (WC: Tardisode 8, Tardisode 9, TV: The Impossible Planet) The Beast possessed the Ood, and made them into his "Legion" in order to besiege the human party of the expedition. (TV: The Impossible Planet) They were defeated when Danny Bartock, the expedition member in charge of them, broadcast a telepathic flare which reduced their field to Basic Zero. This created a "brainstorm" which caused them to collapse. However, their telepathic field began to reassert itself after a time. When the Tenth Doctor broke the gravity field that kept Krop Tor in orbit around the black hole K37 Gem 5, the Doctor was only able to make a single trip in the TARDIS to rescue Ida Scott from suffocation; he was unable to save any of the Ood on the base, who had just been freed of the Beast's control. All perished but were given posthumous honours. (TV: The Satan Pit)

In 4126, the Tenth Doctor and Donna Noble visited the Ood Sphere by happenstance. They found Ood Operations, and decided to learn the origins of the Ood and what or who had turned them into a race of slaves. At the same time, the "red-eye" disease was becoming more and more common. They discovered that the disease was caused by the Ood Brain's subconscious reasserting itself over the Ood thanks to the efforts of a member of "Friends of the Ood" who had infiltrated the company secretly.

Ood Operations' head, Klineman Halpen was unwillingly transformed into an Ood as a culmination of him taking hair tonic deliberately contaminated by his own Ood servant. The Doctor deactivated the field that was suppressing the Ood Brain's telepathy and it sent out a song that was heard by everyone across the three galaxies. Humanity, now knowing the truth about their Ood slaves, returned them to the Ood Sphere, where they were set free and allowed to live in peace. (TV: Planet of the Ood)

Circa 4226, the Ood's development had been unnaturally enhanced, allowing them to build an entire civilisation and extended their mental powers. At the same time, the Ood had nightmares of and of time bleeding. (TV: The End of Time) In response, they sent Ood Sigma to 2059 to contact the Tenth Doctor. (TV: The Waters of Mars) He eventually arrived on the Ood Sphere and telepathically connected to the Ood Council. When he saw the Master, he immediately returned to the 21st century to investigate. The Ood watched him and when he finally began to die, they telepathically sang to him. (TV: The End of Time) The Ood was one of the 11 creatures who appeared in the hologram projection shown by the Atraxi as they were scanning Earth's history to check if it was protected. (TV: The Eleventh Hour)

Undated events
At some point an Ood (later named Nephew) had been transported by a time rift to a bubble universe, where he was severely injured from the journey. He was repaired and taken control of by House to use as a medium to drain another's soul and mind for his plans to remove TARDIS Matrixes. Unlike Auntie and Uncle, Nephew was brought along by House when it took over the Doctor's TARDIS, using him to try and kill Amy and Rory. Nephew was destroyed when the Eleventh Doctor and Idris landed the Junk TARDIS on him, ripping him apart at the atomic level. The Doctor lamented briefly that Nephew was yet another Ood that he had failed to save. (TV: The Doctor's Wife)

At least one Ood was abducted and sent to face its fear in the Minotaur's prison ship. (TV The God Complex)

At one point, Albert Einstein was brought to the TARDIS and was accidentally turned into an Ood by his experimental liquid. However, the Eleventh Doctor was able to reverse this, but the chemical itself gained sentience. (TV: Death is the Only Answer)

The Eleventh Doctor rescued an Ood from the Androvax conflict, with the intent of returning him to the Ood Sphere, but the Ood at one point escaped from the TARDIS and took refuge in the home of Amy and Rory. For the next month or so, the Ood insisted on acting as the couple's butler until the Doctor was able to retrieve him. (WC: Pond Life)

Several Ood worked in the claims department of Psychic Paper Inc. (COMIC: Psychic Paper Inc Claims Department)

The Eleventh Doctor once had multiple Ood on his TARDIS. When the Ood received upgrades to their communicators, which the Doctor described as "all the rage," they stopped serving the Doctor, Amy, and Rory and began playing "bird-throwing games" and trolling the Doctor on Twitter about his eleventh incarnation not being as good as his tenth. (COMIC: An Ood Thing to Say)

Behind the scenes

 * At one stage the Ood were going to be in the episode, 42, where they were to be possessed again, this time by Torajii presumably. (DWDVDF 5)
 * An Ood appeared in a Doctor Who-themed Christmas episode of Never Mind the Buzzcocks, exiting the TARDIS when Phill Jupitus's team asked for a hint and singing the intro to Don't Go.

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