When he was six, Klineman Halpen was taken to the Ood Sphere and saw the Giant Ood Brain within. He had his own personal Ood who looked after him, named Sigma. The stress associated with running Ood Operations made him lose much hair in five years, presumably after he assumed control of the business, and was dosed with hair tonic by Sigma.
When the Ood began being infected with Red-eye, Halpen arrived on Ood Sphere to oversee their eradication and establish control. When the entire Ood "livestock" were infected with this mysterious disease, Halpen ordered the gassing of all affected Ood, and intended to destroy the Giant Ood Brain to contain the Red Eye and kill the Ood.
Ood Sigma led the Tenth Doctor and Donna Noble to the Ood Brain for the final confrontation. When his lead scientist, Doctor Ryder, revealed he was a Friend of the Ood and had spent ten years infiltrating the Company to lower the psychic barrier surrounding the Ood Brain, Halpen threw him into the Brain, which devoured him.
Halpen was sensing defeat and suffering from intense headaches. Sigma revealed that he had used the Hair Tonic to dose Halpen with Ood graft suspended in a biological compound, turning him into an Ood as punishment for his attitude towards Oodkind. Sigma declared he would look after Halpen.
Halpen thought of Ood as nothing more than slaves and treated them like animals. However he was fond of Ood Sigma, mistakenly thinking Sigma was loyal to him. During the Ood revolution, Halpen told Sigma to go and join the other Ood while he still could. Until that moment however, Halpen thought of Sigma as nothing more than a servant. When he realised Sigma was not loyal to him he was horrified and his horror increased when he found himself transforming into an Ood.
A vain man, Halpen repeatedly used what he thought was hair tonic to prevent going bald. This resulted in him getting turned into an Ood. Halpen also said he'd never shot anyone before and also added that he didn't think he would enjoy it, but this didn't stop him from aiming a gun at the Doctor and Donna. He also didn't hesitate to push Doctor Ryder into the Ood Brain after realising that Ryder was a Friend of the Ood.