Kamelion

Kamelion was a shape-changing android. Used by to impersonate King John, he later travelled as a companion to the Fifth Doctor. (TV: The King's Demons) This continued until his destruction after he had again fallen under the influence of the Master. (TV: Planet of Fire)

However, this was not the end for him. He gained and lost a new host body, (PROSE: The Ultimate Treasure) had a child with the Doctor's TARDIS (PROSE: The Reproductive Cycle) and used his mental link with the Doctor to allow the Master to trap the Doctor within a dreamscape. (AUDIO: Winter)

Abilities
Kamelion was created from structure mathematics via Block Transfer Computations. As such, he was able to change his appearance and form. Not only could he masquerade as various humanoids, but he could actually change his size and form at will, at various points taking such forms as a Gubbage Cone with many tendrils and a fifty-foot tall version of his standard form. He was also able to change his hands into weapons. (PROSE: The Crystal Bucephalus)

Creation
The Kamelions were created by the Gelsandorans (PROSE: The Ultimate Treasure) as weapons of war during their invasion of the planet Xeriphas before leaving. Not knowing why they left, Kamelion shut down his consciousness. When became trapped on Xeriphas, (TV: Time-Flight) he discovered Kamelion had been left behind by previous invaders. He used the android to impersonate many beings across the cosmos, all the while causing Kamelion to develop a conscience. In his next encounter with the Fifth Doctor, he was using Kamelion to impersonate King John, in order to pervert history by preventing the signing of Magna Carta. (TV: The King's Demons)

Travels with the Fifth Doctor
The Doctor freed Kamelion from the Master's control and invited him to join the TARDIS crew, although Turlough and Tegan were uncomfortable with him. (TV: The King's Demons)

Kamelion preferred to remain in the TARDIS for fear of being taken over by a stronger personality and used against the Doctor, after believing he had overcome his programming only to be made to kill someone. (PROSE: The Crystal Bucephalus) However, he helped rescue the Doctor and Turlough during a trip to the Moon with a Victorian lunar expedition in 1878. Initially confined to the TARDIS by a force field preserving an atmosphere on a lunar park, Kamelion later left the park and rescued the Doctor as he was dying of asphyxiation on the surface. Later, he helped the Doctor and Turlough salvage weapons to use against the ruthless Vrall, and posed as the spirit of the deceased Prince Albert to convince Queen Victoria to abandon the space program. (PROSE: Imperial Moon)

At some point, a picture of Kamelion was obtained by UNIT, and was present in the Black Archive by UNIT. (TV: The Day of the Doctor)

Kamelion fell under the Master's remote influence in Lanzarote and assumed the shape of Peri's stepfather, Howard Foster, after picking up on her thoughts. When the Master gained complete control over him, Kamelion assumed the form of the Master. The Master used Kamelion to reverse an accident with his TCE that had shrunk him and his lab. The Doctor and Peri tried to return Kamelion to his own control and his robotic form. When the Master was restored to his normal size, Kamelion was in agony over his possession and persuaded the Doctor to kill him. His final earthly words were: "Destroy me... please..."(TV: Planet of Fire)

Afterlife
A little of Kamelion's personality survived as a result of his interfacing with the TARDIS. When the ship arrived on Gelsandor, the natives gave him a new body, only for him to sacrifice himself to save the Fifth Doctor and Peri. (PROSE: The Ultimate Treasure)

As the Fifth Doctor lay dying from spectrox toxaemia, enough of Kamelion's mental link to him existed to allow to use Kamelion to trap the Doctor in a dreamscape within his own mind, slowly destroying his will to regenerate. In this trap, Kamelion took the form of Anima, the Doctor's wife and the mother of his children. Thanks to the encouragement of Nyssa and her husband Lasarti, who were also mentally linked with him, the Doctor was able to see through the illusion. Freed from the Master's control once again, the psychically linked aspect of Kamelion in the Doctor's mind was able to join Nyssa and the Doctor's other companions from across space and time to free him from the trap so he could regenerate. (AUDIO: Winter)

Later, Kamelion and the TARDIS had a child together, which was raised by the Sixth Doctor and Peri Brown. It developed into a double of Peri and took her place on Earth while the real Peri travelled with the Doctor. (PROSE: The Reproductive Cycle)

Other information
Kamelion assumed the shapes of John of England, Tegan Jovanka, (TV: The King's Demons) Arrestis, Lassiter, (PROSE: The Crystal Bucephalus) Albert, (PROSE: Imperial Moon) Howard Foster, the Fifth Doctor, (TV: Planet of Fire) and Red. (PROSE: The Ultimate Treasure)

While dying from the effects of spectrox toxaemia, the Fifth Doctor hallucinated about many individuals, including Kamelion, urging him to live. (TV: The Caves of Androzani)

Behind the scenes

 * According to the featurette Kamelion - Metal Man, included on the DVD release of The King's Demons, the robot used for Kamelion was not custom-made for the series, but was a device discovered by producer John Nathan-Turner when he was searching for a possible successor to K9. According to the featurette, script editor Eric Saward and Peter Davison were extremely sceptical that the robot would work as an ongoing companion due to its frequent malfunctions.
 * Kamelion's mouth was designed to move in sync with the pre-recorded dialogue by Gerald Flood.
 * Kamelion only appeared twice in the series; further appearances were impractical due to the special effects required. A scene involving Kamelion was filmed for part one of The Awakening, but was edited out before transmission due to the episode overrunning. As a result, there are no references to Kamelion in any episodes between The King's Demons and Planet of Fire, not even in The Five Doctors, which occurs immediately after the events of Kamelion's debut. Kamelion's software designer, Mike Power, was killed in a boating accident not long after the robot was accepted to appear on the series, and as he had never made fully documented operating notes, this made operation of the prop considerably difficult.
 * According to Peter Davison in the Metal Man featurette, any sign of regret shown by him/the Doctor during Kamelion's "death" scene was pure acting. He was in reality gleeful to be done with the troublesome prop.
 * A box set containing The King's Demons and Planet of Fire was released under the title Kamelion Tales.