Space pig

The "space pig" (PROSE: Operation London, TV: Exit Wounds) was a pig from Earth that was kidnapped and genetically modified by the Slitheen family into a humanoid form with an enhanced brain. It was initially believed to be an alien.

Biography
After its modifications, it was set into a spaceship that was launched from Earth in the North Sea and rigged to land in the Thames twelve hours later. This was intended as an excuse to put the British government on red alert for an alien invasion. (TV: Aliens of London) Immediately after the crash, UNIT personnel discussed it on a secure operations board on the UNIT website, with Corporal J Frinkstein informing the other personnel that he had liaised with the Army, and shortly after, they had reached the craft, with the space pig inside being discovered; Frinkstein considered it to be sweet, but Major Jenny Maguire advised caution nevertheless. The space pig was taken to the xenobiologists at the Albion Hospital. (PROSE: Operation London)

However, the pig was only examined by a single individual, (TV: Aliens of London) Toshiko Sato, a Torchwood Three employee posing as a doctor, although she was only filling in for Owen Harper, who was incapacitated due to a hangover. (TV: Exit Wounds) squidbaby23 was seemingly able to take a picture of the alien, which she considered to be "amazing", (PROSE: Alien landing confirmed) before the alien was shot and killed by a soldier while running around the hospital, scared out of its wits, despite the Ninth Doctor wanting it to survive. (TV: Aliens of London)

Legacy
squidbaby23 also created a drawing of the alien creature, and sent it to Mx — the webmaster of Who is Doctor Who? — along with the picture she took earlier, however she refused to reveal to Mx how she obtained the latter picture, leaving Mx to speculate about the creature's nature on his website. (PROSE: Alien landing confirmed)

Just prior to his regeneration, the Ninth Doctor looked back on his life, remembering the Slitheen's modified pig. (PROSE: Shortness of Breath)

Behind the scenes
The space pig was never named in Aliens of London, only referred to as "Alien" in the credits. The name space pig was given to it by the short story Operation London from the Operations Board series on the U.N.I.T. tie-in website and later in the Torchwood television story Exit Wounds. Conversely, the The Doctor's Data series in Doctor Who Adventures, Character Options' Micro Universe figures, Doctor Who: Battles in Time — Exterminator trading cards, and the Doctor Who: Figurine Collection named it the "Pig Pilot". Doctor Who: The Inside Story used "Space Pig".

Alien-Schwein Космическая свинья