Captain Cook is the secondary antagonist in the Doctor Who story "The Greatest Show in the Galaxy". He is a renowned Intergalactic space traveller who patrolled the galaxy alongside his companion Mags before eventually dropping his friendly façade and instead abusing his ally's lycanthropy to his advantage .
He was portrayed by the late T. P. McKenna.
Captain Cook was a famous intergalactic explorer with a high opinion of himself and a low opinion of most others. He had rescued the werewolf Mags from Vulpana and made her his assistant but saw her more as a specimen to analyse than a person. He was curious about the Psychic Circus' talent contest and headed to the planet Svartos with Mags, where they met up with the Doctor and Ace, who he bored with stories of his travels. When they were attacked by an abandoned robot, Cook did nothing to help as the others fought it. They then investigated the Circus' tour bus where Cook directed the robotic Bus Conductor to attack the Doctor instead of him.
Cook and Mags travelled on together to the Circus tent where they quickly learned the truth: That the participants in the talent contest were killed when they failed to entertain. They were imprisoned with another visitor, Nord. Cook made no attempt to warn the Doctor when he arrived, letting him be captured as well since he intended to delay his entrance into the ring as much as possible. He had Nord go in first by tricking him with a double-headed coin, leading to his death.
When the Doctor and Mags escaped, Cook not only refused to go with them but helped the clown robots track them down. However, Mags helped the Doctor escape and the Chief Clown made it clear that Cook would take his place in the ring. Instead, Cook managed to convince Whizzkid, one of his admirers, to go in first, causing him to be killed.
The Doctor surrendered to the clown robots and convinced Mags and a reluctant Cook that they should all go into the ring together. However, Cook double-crossed the Doctor and had the Ringmaster produce a moon lighting effect that triggered Mags' transformation. He tried to get Mags to attack the Doctor but the Doctor managed to appeal to her true personality and she instead attacked Cook and killed him.
Cook's body was later reanimated by the Gods of Ragnarok, the power behind the Psychic Circus, to stop Ace, Mags and Kingpin getting the medallion the Doctor needed to defeat them into their dimension. Cook failed and walked off a cliff edge into the vortex leading to the Gods' dimension.