Coker is a mechanical man in the Power Plant of Mars responsible for mining the coal and putting it on the conveyor belt. When the Avatar met him in Martian Dreams, Coker was unable to do his work, since the conveyor belt was broken and out of power. Coker had only very simple programming, and knew nothing else apart from describing his job. After the Avatar had fixed the conveyor belt and jump-started the furnace to power the belt, Coker returned to his job to power the planet.