- For Theta Sigma, see separate entry.
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 "Sigma" (Σ) on the right side of his uniform.
Profile
For some time, Sigma had remained by Halpen's side while other Ood succumbed to Red Eye. He led the 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; while the Red Eye 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. (DW: Planet of the Ood)
Behind the Scenes
It is rumoured that Ood sigma will feature partially in one of the 2009 specials as actor Paul Casey was seen on set wearing the ood prosthetic and the costume worn by the character.