O is for... Ogrons

Brutal ape-like beings, they were natives of an obscure planet in a relatively unexplored region of space, on the edge of the Earth and Draconian Empires. Fiercely loyal, though low in intelligence, they made ideal servants for other races – gaining a reputation as mercenaries. When the Daleks changed Earth history in order to make their failed 22^nd Century invasion of Earth a success they employed the Ogrons as a security force. The human Controller wished to employ his own kind, due to the dim-witted nature of the Ogrons, but the Daleks overruled him.
When a guerilla group travelled back to the 20^th Century to prevent their timeline from taking place, Ogrons were sent back to stop them. Though armed with superior weaponry, they preferred brute force to kill or capture their enemies.
The Doctor discovered that they had one physical weakness – being susceptible to a blow on the top of the head.
The Doctor was able to put history back on course, and the timeline was deleted.

In 2540 the Daleks used the Ogrons as part of their scheme to pit the human and Draconian empires against one another, after being approached by the Master. He had created a device which preyed on the fear centres of the mind, causing its victims to see the thing they feared the most.
He used the Ogrons to attack spaceships belonging to both groups, ensuring that there were survivors from every raid. His device made each race see the other instead of the Ogrons. Tensions were always high between the two empires due a bloody space war which had been fought only 20 years before. Initially unaware of who was behind the scheme, the Doctor and Jo witnessed an Ogron raid when the TARDIS arrived on a space freighter – but the Earth authorities refused to believe them. The TARDIS was brought to the Ogron planet along with other spoils of the raid – alerting the Master to the Doctor’s presence. Ogrons were sent to Earth to free him from prison – the Earth people seeing them as Draconians.
Later, on a mission to free the Master from capture by the Draconians, one of their number was left behind and the Draconian Emperor realised the truth of the Doctor’s claims. The Earth authorities were also finally convinced and a mission was launched to the bleak, rocky Ogron planet.

There the Doctor discovered that the Ogrons worshipped a monster which preyed on them. In appearance it was a huge, shapeless orange mass.

Jo stole the Master’s hypnotic device, and the Doctor used it to appear as a Dalek to trick an Ogron guard into releasing his party from a cell, and later to appear as one of the monsters to cause a whole party of Ogrons to flee in terror.

Played by: Stephen Thorne, Michael Kilgarriff, Rick Lester. Appearances: Day of the Daleks (1972), Frontier in Space (1973).

• Both appearances by the Ogrons were directed by Paul Bernard. The script for  Day of the Daleks simply described "monsters" and it was he who decided that they should be ape-like. The description of them as "guard dogs" for the Daleks had led Barry Letts and Terrance Dicks to think of them as dog-like.
• Rick Lester played an Ogron in both stories.
• John Friedlander designed the half-masks, which were made by make-up trainees.
• Some of the non-speaking Ogron extras had heads too large for the masks, and they had to be split at the back.
• The company which made the Ogron-eating monster prop mistakenly called it an "Oberon-eating" monster in their literature.
• The prop was deemed so poor that its appearance was kept to an absolute minimum. It was originally to have been used in studio for the final scenes.