all Ood together. 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. Ood Sigma returns as part of the 2008–10 specials in the episode "The Waters of Mars", where he appears at the end of the episode in an attempt to contact the Doctor. The Ood also appear in the following episode, the two-part story "The End of Time". In this episode, the Doctor finally accepts Ood Sigma's message and returns to the Ood Sphere 100 years (in their time line) after having freed them in "Planet of the Ood". The Doctor discovers that the Ood's civilisation has advanced too rapidly, and that the Ood have developed the ability to see and project themselves through time itself. The Ood reveal that this is a consequence of time "bleeding", and the elders of the Ood show the Doctor the dreams and prophesies they have been seeing. At the end of part two, Ood Sigma appears again to the Doctor and gives him the encouragement to return to his TARDIS to complete his regeneration into the Eleventh Doctor. The End of Time also introduces an Ood Elder, who has an exposed brain, crescent-shaped ears and yellowish tentacles. A single Ood referred to as Nephew appeared in the series six episode "The Doctor's Wife". Nephew is under the influence of an alien entity called House. Nephew is killed when the Doctor and Idris land a TARDIS console in the exact spot he was standing, vaporising him instantly. The Doctor remarks that Nephew was "another Ood I failed to save", a reference to his previous encounters. Nephew's eyes glow green when possessed, a change from the red in previous episodes. In the mini episode "Death is the Only Answer", the scientist Albert Einstein is transformed into a red-eyed Ood after ingesting a mysterious liquid. The possessed Ood repeats the phrase "Death is the only answer" before being transformed back into Einstein. A scene cut from "A Good Man Goes to War" would have seen the Doctor meeting up with Ood Sigma again. Russell T Davies is still credited at the end for the scene despite it being cut. In