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. He blamed the stress associated with running Ood Operations for some significant hair loss over the course of five years, presumably after he assumed control of the business. He took what he thought was hair tonic to address the problem. 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. He 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 a final confrontation. Halpen's lead scientist, Doctor Ryder, revealed that he was a Friend of the Ood and had spent ten years infiltrating the Company to lower the telepathic barrier surrounding the Ood Brain. This prompted Halpen to throw 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. (TV: Planet of the Ood)
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 rebellion, 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. 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 his transformation into an Ood, at the hands of Ood Sigma. Halpen said he'd never shot anyone before, adding that he didn't think he would enjoy it. This didn't stop him from aiming a gun at the Doctor and Donna, however. He also didn't hesitate to push Doctor Ryder into the Ood Brain after realising that Ryder was a Friend of the Ood. (TV: Planet of the Ood)