Sigma

Ood Sigma was the personal Ood of Halpen, manager of Ood operations. He was the most important Ood. He dosed Halpen with Hair tonic as he was bald. Sigma traveled with Halpen to Ood operations. Sigma remained by Halpen's side even when all the other Ood were infected with Red Eye. Sigma led the Doctor and Donna Noble to the the room containg the Giant Ood Brain. There Sigma revealed to Halpen he had been dosing him with a liquid that turned him into an Ood using the hair tonic. Sigma then declared he would look after Halpen. (DW: Planet of the Ood)