The Ood return in the Series 4 episode "Planet of the Ood", where it is revealed that they are not born to serve but are an enslaved race. The Ood translation spheres actually replaced their hind brain which had contained their individual personalities. The Doctor successfully frees the Ood by releasing the Ood hive mind, which connects all the Ood with a telepathic link. The hive mind had been sequestered from the Ood for 200 years by Ood Operations, the corporation that processed the Ood slaves. The possessed "red eyed" Ood reappear in this episode, running amok at the behest of the hive mind. After being freed, all Ood across the universe are returned to the Ood Sphere. While there, Ood Sigma refers to Donna Noble as "Doctor-Donna" and prophesizes that the Doctor's "song" will soon come to an end.