Ood Sigma Σ ( Sigma ) was the personal Ood of Klineman Halpen , the manager of Ood Operations . This particular Ood could be identified with the large Greek letter " " ( Σ ) on the right side of his uniform . Biography . In 4126 , the Ood brain managed to reconnect to Ood Sigma despite his link having been severed through the translator orb . Sigma was made a focus of the Brain ' s intelligence and mercy , and also its representative , in a sense . This allowed him to function as an individual and drug Halpen ' s hair tonic with Ood graft to transform him in to an Ood . For some time , Sigma had remained by Halpen ' s side while other Ood succumbed to red - eye . As Sigma was already reconnected to the Ood Brain , he was immune to the rage and anger which subsequently infected the other Ood . He led the Tenth Doctor and Donna Noble to the room containing the Ood Brain . There Sigma revealed to Halpen he had been dosing him with a liquid , disguised as hair tonic , which turned Halpen into an Ood . While the red eye - infected Ood had been " contaminated " by the Ood Brain ' s anger , Sigma had become the focus of the brain ' s patience as he transformed Halpen . Sigma declared that the Ood would look after Halpen . As the Doctor and Donna departed , Sigma assured them that they would always be remembered as friends of Ood - kind , and would have a part in the song for as long as the Ood existed . However , he ominously remarked the Doctor ' s song would soon come to an end . ( TV : " Planet of the Ood " ) The Doctor saw a vision of Sigma in 2059 , shortly after the suicidal death of Adelaide Brooke . ( TV : " The Waters of Mars " ) The vision was actually Sigma trying to summon the Doctor to the 43rd century , as the Ood were experiencing visions of the Master . When the Doctor responded to his message , Sigma seemed disturbed that the Doctor had taken so long . He told the Doctor that it took them 100 years to make Ood Sphere better . The Doctor was amazed and somewhat worried at the progress they had made in 100 years . Sigma took him to the Ood Elder to try to warn him of the impending danger . When the Ood held hands , Sigma did not . When the Elder foretold the " end of time " , the Doctor left abruptly . After the events that led to the Doctor and saving the universe from Rassilon and the other returning Time Lord s , the Doctor bade farewell to all of his companions . In 2005 , after briefly talking to a younger Rose Tyler , the Doctor began to experience increased effects of his impending regeneration . Just before the Doctor returned to the TARDIS , Ood Sigma appeared to him again . He told him that the universe would sing him to his rest , and that while this song was ending , his story would never end . The Ood all joined together in song as the Doctor stumbled into the TARDIS to regenerate into his eleventh incarnation . ( TV : " The End of Time " ) Ood Sigma welcomed the Eleventh Doctor to the Ood Sphere when he returned the fifteen Ood who were prevented from going home on the " The Devil ' s Eye " . ( COMIC : " Time of the Ood " ) Personality . Ood Sigma was a very patient Ood , and , as he was the first Ood to reconnect with the Ood brain , he was the only known Ood who was immune to the fits of rage that infected other members of his species . Klineman Halpen mistakenly thought this was because of loyalty . He was able to act independently instead of doing what every other Ood did . A cunning creature , Sigma acted like a loyal servant whilst secretly giving Halpen a liquid that would turn him into an Ood . He grew to think of the Doctor and Donna as his friends and stood between them and his former master when Halpen aimed a gun at them . Despite his dislike of Halpen , Sigma said he would look after him after turning him into an Ood . ( TV : " Planet of the Ood " ) When the Doctor and Sigma were reunited , the Doctor told jokes in an attempt to liven things up . Sigma remained impassive and the Doctor grumbled about him possessing no sense of humour . However , Sigma later showed the Doctor further kindness by easing his transformation into his next incarnation . ( TV : " The End of Time " ) Behind the scenes . According to " The Brilliant Book 2012 " , Sigma was helping the Doctor in his attack on Demon ' s Run , explaining why Russell T Davies is given credit for creating the Ood in " A Good Man Goes to War " even though no Ood was seen .