Robots are the second creatures encountered in Zombotron 1, in Zombotron 2 they are the third, and in Zombotron 2: Time Machine, they are the fourth. Robots were used for mining in the colonization of the planet, but once abandoned a coding error made them attack living things.
Normal robots have more health than zombies and carry a mining tool. They can show up in red or gray colors. They have a bucket-shaped head with a red visor and a purple screen on their chest.
Red Robots have a rusty red color and are slightly easier to kill than the gray ones. They can be killed by three shots from a pistol, rifle, or machine gun and one shot from a shotgun. They carry shovels to attack the hero.
The gray robots carry pickaxes to fight and are harder to kill than the red ones. A pistol can kill them in four shots and a shotgun can kill them in two shots. One of them is Harry, Fina's robot.
Although not technically a robot, turrets are still machines and could be considered robotic. Turrets move on wheels and can only face/move in one direction. Turrets have a large minigun, and will rapidly shoot at anything that moves. You need to shoot the light on top of the turret to destroy it or keep on shooting it. They explode after (roughly) 2 seconds when killed. They drop two coins. They are no longer in any levels after level 9 in Zombotron. They cannot be killed by enemies (except for other turrets).
Defense Robot/Golden Robot
These robots have a grenade launcher on their side of their arm. They use it as a melee weapon or a long range weapon. They are seen in Zombotron 2. They are very deadly, as one shot from their grenade launcher will kill an unarmored player. They are best dispatched with headshots (although explosives will do just fine). They are encountered after the grey and red robots. They fire the same grenades as the grenade launcher.
Robomachine (scientist's variant)
This mechanical abomination is the result of the scientist's researches. It has a yellow head with an antenna on it and a yellow torso and is armed with a back-mounted grenade launcher. The robot has grey arms and legs and is one of the biggest enemies. It is the final boss in Zombotron 2. It shoots multiple grenades at once and throws fireballs akin to the Boss Monsters' that explode on contact. It also attacks in close combat and is the most powerful enemy in the game.
Robomachine (red variant)
This variant is encountered in Zombotron 2: Time Machine. When the hero, Fina and her father are about to leave the planet with the capsule, the robot destroys the wall of the garage and starts pursuing their truck. The Robomachine is rather slow, but if it gets close enough to your vehicle he can easily destroy the capsule. In the last level of the game, the hero finds out that the robot has reached the truck and killed Fina's father (whose bloodstained body can be seen on the truck) and perhaps Fina. Destroying this boss is not needed to complete the game, as the Robomachine does not even notice the player unless he attacks first; if he does so, the boss fight will begin and several Biobots and mutants will join the robot in order to kill the hero.
The red variant of Robomachine is a recoloured version of the scientist's invention: its torso and head are red instead of yellow. It may be assumed that this variant has not been created by the scientist, but by someone who recycled the projects of the yellow Robomachine defeated in the previous game: in fact, when the player destroyed the latter, the scientist said that "years of work have been destroyed", so that was probably the only prototype created by him.