Krikkitman

The Krikkitmen were humanoid androids from the planet Krikkit. They were produced for and started the Great Krikkit War. The Krikkitmen appeared to be sentient, but were in fact simple computers disguised as androids. They were white in colour (resembling cricket whites), were able to fly, and carried multifunctional battle clubs (appearing like a cricket bat) which could knock down buildings, fire rays, and launch devastating grenades (similar to cricket balls). In fact their design subconsciously but directly affected that of the sport cricket.

History
A dust cloud separated them from the rest of the universe, so the Krikkitas thought that they were the only beings in the universe. After learning that they weren't (when a spaceship crashed on their planet), they set out to destroy the universe. They created androids and made ships and sent them off as perfect killing machines. It turned out that this was a ploy by a bored supercomputer, Hactar. After the Krikkit Wars, the Time Lords stored the Krikkitmen in their own dimension on Shada as they were believed to be sentient. A rogue Krikkitman later freed them and set out to continue their goal, but the Fourth Doctor and Romana prevented this. They did so by tricking the Krikkitmen into turning themselves on and off repeatedly until they exploded.

While Krikkit was sealed in the Slow Time Envelope, the Krikkitas attempted to reproduce more Krikkitmen. While they didn't succeed, several working models existed such as Sir Robot, who did not have the intent to kill. (PROSE: Doctor Who and the Krikkitmen)