Doctor Ogron
Doctor Ogron was an Ogron who had been experimented on by the Dalek Overseer, and given the Doctor's personality.
He arrived on Gallifrey in the Doctor's TARDIS and claimed to be the Doctor, having all of his memories. Analysis of his DNA also turned up sufficient similarities to the Doctor's own current DNA, with any differences little more than the kind of differences the Time Lords would expect after a particularly traumatic regeneration. He was sent with the Twelve on a mission to find the Eighth Doctor and Bliss and investigate the Daleks' operations on the Ogron homeworld. Bliss called him "Doctor Ogron" to not confuse him with the Doctor, to which he replied that he would call her "Bliss Human".
Although the Doctor refused to believe the Ogron could be anything like himself, he eventually came to trust his new counterpart, knowing that he would escape with Bliss without having to say anything. When the Doctor and the Twelve were captured, the overseer conducted the experiment which transferred the Doctor's essence to one of his workers, and which created the Doctor Ogron personality. When the younger version of Doctor Ogron escaped, the Doctor sent him to Gallifrey in his TARDIS to maintain the timeline.
Meanwhile, the Doctor Ogron who had escaped with Bliss managed to convince many of the natives of The Planet to rebel against the Daleks. When his first attempt to rally the Ogrons failed, he sought the assistance of the crab-like creatures whom the Ogron's worshipped as Gods, thus gaining the Ogrons' obedience.
Doctor Ogron was exterminated by the Daleks during the attack on the Dalek complex, which the Doctor and the Twelve had also rigged to explode, using the Daleks' own weapons against them. Although he regenerated soon after, by this time the Doctor, Bliss, and the Twelve had escaped, and so he escaped in one of the sentient TARDISes. (AUDIO: Planet of the Ogrons)