Series 4 (2008)
Episode title: Planet of the OodFeaturing: Tenth Doctor
Companions: Donna Noble
First shown: 19th April 2008
Related articles: Ood
Guide: The Doctor takes Donna to the planet of the Ood, to visit some old friends.
At the start of the episode, the duo encounter an injuried Ood in the snow, dying. As the Doctor and Donna go to help, the Ood's eyes turn red and it lunges for the Doctor, which startles him. He muses about the last time he met the race.
The Doctor and Donna go to a complex, owned by Ood Industries, who have been selling slave Ood's since 3914. The 'red-eye' has been happening to every Ood all over the planet, and it is causing them to kill humans. Donna becomes increasingly sympathetic towards the Ood, as does the Doctor, who notes that no race could possibly naturally evolve to serve.
The duo find an uncultivated Ood, who does not have a translation device in his hand, but his hind brain. It is revealed that these are removed, and replaced with the translation device when the Ood grows old enough. It is the removal of the hind brain that makes the Ood subservient.
The Doctor discovers a large brain in a warehouse, which is the collective consciousness of the Ood, and is controlling both them and their 'red-eye' - which presents itself as different emotions, such as anger.
Or paitence. It is revealed that Ood Sigma (Halpen's personal Ood) has been poisoning him in his hair replenishment potion, to convert him into an Ood, which happens at the end of the episode. At the very end of the episode, Ood Sigma says that both the Doctor and Donna will be named in the Ood's song, but also notes that the Doctor's song may soon end.