Sleeper agent
From Tardis Wiki, the free Doctor Who reference
Sleeper agents are soldiers used before an invasion. They are often modified to resemble the species that is to be invaded, and are used to gather intelligence on the species and planet.
A group of sleeper agents for one species was officially known as Cell 114, of which very little was known. The sleeper agents of this species had implants which could take the information and transmit it to the main invasion fleet. These implants even had built-in weaponry such as spikes and explosives. (TW: Sleeper)
