"They don't exactly look friendly."
– Moninger, 2153 ("Regeneration")

Doctor Moninger was a researcher with the Earth Sciences Institute and was a member of the A-6 excavation team, an Arctic Archaeology Team, during the 2150s. In 2153, Moninger was among the archaeologists who discovered the debris from a crashed Borg sphere in the Arctic Circle on Earth.

In his lab, Moninger later examined the corpses of two Borg drones found among the wreckage. He found them to be of differing species, as well as heavily augmented with technological devices and tools. Once he had had the bodies in the lab long enough to begin to warm up, he discovered that the nanotechnological devices in their blood were actually functional and active – repairing the biological and technical components of the bodies.

After receiving delivered coffee in a thermos, Dr. Moninger dismissed his aide to repair a heating unit. This left him alone with the two Borg drones, one of which came to life shortly thereafter. Moninger grabbed a scanner, but couldn't get to a weapon quickly enough to defend himself and was infected with their nanotechnology. He was assimilated along with his colleagues Rooney and Drake. The assimilated researchers and revived drones left Earth in their vessel Arctic One (which was also gradually assimilated), presumably on a course for Borg space, and were later killed when their ship was intercepted and destroyed by Enterprise NX-01. (ENT: "Regeneration")

Moninger was played by actor Chris Wynne.
In the script of "Regeneration", Moninger was described as being in his thirties, during the events of the story. Chronologically, Moninger was likely the first human ever to be assimilated by the Borg, albeit a 24th century drone.
His survival suit from this episode was later sold off on the It's A Wrap! sale and auction on eBay. [1]