Android

Androids are artificial beings designed to look and behave like humans, unlike robots, which, even if humanoid, are easily distinguishable from humans; while the term "android" actually refers to a robot designed to resemble a human (andro) male, and the term "gynoid" is the correct term to use for a robot designed to look like a human (gyno) female, "android" has been accepted over time as a 'catch-all' description for a human-looking robot of either gender. Androids are created in the Commonwealth, which apparently has enough technology and resources to make large numbers of synthetic humans (according to Dr. Zimmer in the game).

Some of the self-aware androids in the Fallout 3 Game Setting occasionally attempt to escape their masters and have to be hunted down by specially trained trackers -an apparent homage to the sci-fi classic, Blade Runner.

Appearances
At least five androids appear in Fallout 3. Two of them are:
 * Harkness
 * Armitage

They both have a small light source in their eyes. It's not dependent on external lights and can be seen from a greater distance than the usual reflection of light from eyes in the game.

Based on the information above, it appears that the Mercenary at Craterside Supply is also an android

Related quests

 * The Replicated Man