Host body

A host body was a body used, infected or possessed by another creature, usually one who was incorporeal or very small. In some cases the possession was fatal to the host.

While many life-forms on Earth exist in a symbiotic or parasitic relationship, the idea of 'body-snatching' aliens taking over Earth in a month or a year is biologically impossible: symbiotic/parasitic relationships evolve over thousands of years, and are specific to the particular species involved.

Host bodies

 * Lady Cassandra used several bodies as hosts, including Rose Tyler, the Tenth Doctor and Chip when she had left her own body, through the use of a psychograft. (TV: New Earth)
 * Eknodines used many bodies as hosts, including Poggit, Hamil and Nainby. (TV: Amy's Choice)
 * The Isolus child used Chloe Webber as a host body. (TV: Fear Her)
 * The Gorgon had used the Abbess as a host body for a long time and chose Sarah Jane Smith as a replacement. (TV: Eye of the Gorgon)
 * The Sex Gas possessed the body of Carys Fletcher. (TV: Day One)
 * Judson and Sorin acted as the host bodies for Fenric. (TV: The Curse of Fenric)
 * Toby Zed and various Ood were possessed by the Beast. (TV: The Impossible Planet / The Satan Pit)
 * Sarah Jane Smith was possessed by an Eight Legs. (TV: Planet of the Spiders)
 * The Seventh Doctor was temporarily possessed by the Timewyrm. (PROSE: Timewyrm: Revelation)
 * The Gelth took many corpses in Gabriel Sneed's mortuary as host bodies, including Mr Redpath, his grandmother, Mrs Peace and Mr Sneed. (TV: The Unquiet Dead)
 * The Host was a human boy who was infected by a lupine wavelength haemovariform. It had survived a crash landing on Earth by passing into the bloodstream of several hosts and adapting through the generations. (TV: Tooth and Claw)
 * The High Priestess of the Sibylline Sisterhood was a host body for a Pyrovile in an early stage. (TV: The Fires of Pompeii)
 * Sky Silvestry and the Tenth Doctor were possessed by the Midnight entity (TV: Midnight)
 * The Mayfly needed host bodies as they grew. It needed a perfect host and so cleared the body of all imperfections. (TV: Reset)
 * The Nostrovites need a host for their eggs as a third member of their reproduction process. (TV: Something Borrowed)
 * Meglos used an "earthling" as a host body to impersonate the Fourth Doctor. (TV: Meglos)
 * Androvax possessed the body of Sarah Jane Smith. (TV: Prisoner of the Judoon)
 * Kroagnon possessed the body of the Chief Caretaker to escape his imprisonment in the basement of Paradise Towers. (TV: Paradise Towers)
 * Wirrn gestated inside host bodies and absorbed the intellect and memories of their hosts. (TV: The Ark in Space, AUDIO: Wirrn Dawn)
 * The Fourth Doctor and several crew members of the Bi-Al Foundation and Titan Base were hosts for the Swarm led by the Nucleus. (TV: The Invisible Enemy)
 * Four townspeople were apparently killed and had their bodies taken over by the Family of Blood. (TV: Human Nature/The Family of Blood)
 * The Torajii sun used number of host bodies, including the Tenth Doctor, to destroy the ship that drained her power. (TV: 42)