A is for... Arcturus

One of the alien delegates to the planet of Peladon, sent to decide on its admittance to the Galactic Federation. Like Alpha Centauri, this may not be its real name - as it is supposed to represent that solar system, though both responded to the titles as though they were their actual names (a TARDIS translation perhaps).
Arcturus was a small creature - only a tentacled skull visible - encased in a large mobile life support unit. This unit had a powerful disintegrator weapon built into it, and it felt no compunction in destroying its host's fixtures and fitting demonstrating its capabilities. Arcturus appeared to favour the admittance of Peladon, and sided with the Ice Warriors against the vacillating Alpha Centauri on a number of occasions. This was significant, as Mars and Arcturus had once been old enemies.
High Priest Hepesh was busy trying to sabotage the process behind the scenes, in order to protect the planet's ancient customs and superstitions. Blame was being put upon the Ice Warriors for these acts, and this included an attack on Arcturus. Part of its life support unit was stolen, later found by Jo Grant in the Martians' quarters, but the Doctor was able to make repairs. The Doctor knew that this sabotage had never been life-threatening.

Hepesh tried to engineer the Doctor's death in mortal combat with the King's Champion - Grun. When it looked like this scheme had failed, Arcturus attempted to shoot the Doctor. It was destroyed by the Ice Warrior sub-delegate Ssorg.
It transpired that Hepesh had entered into a secret deal with Arcturus. The planet would fail to join the Federation and Arcturus would gain a lucrative exclusive trade deal in return for protecting Hepesh's cherished old ways.

Played by: Murphy Grumbar (body), Terry Bale (voice). Appearances: The Curse of Peladon (1972).

• Grumbar was best known as a Dalek operator, though he also operated a Mechonoid in The Chase, a Gellguard in The Three Doctors, and appeared as one of the Functionaries in Carnival of Monsters. He was sometimes credited as Peter Murphy. He died in 1991.