Android Dummy
Android Dummy is a hoax plotted by Mortimer McMire. Android Dummy was a robot controlling the Mangling Machine, its purpose was to make Keen think he has succeed destroying Mortimer, and thus give Mortimer more time to make his plans come true and keep Keen's attention elsewhere.
Android Dummy is actually the only picture of Mortimer ever seen — beside his helmet that can be found in Keen 5, and the "Grand Intellect" picture found in Vorticon homes which is only a silhouette —, assuming he has made it to resemble his features and style of clothing. He is first mentioned in Keen 5, and again in Keen 6.
The intelligence and knowledge of the Android is debatable; it is definitely capable of holding an intelligent conversation and appears to know at least a limited amount about Keen and his past. The android also appears able to have (or fake) emotions, deliberately goading Keen to make him angry. There are hints in the Keen 3 tileset that the android was supposed to be shocked when defeated, which is also indirect evidence of its "humanity".
It is unknown to what extent the android and the Grand Intellect — Mortimer's assumed name while ruling the Vorticons — are the same person. It is possible that the Grand Intellect was really the Android Dummy all along, or that the android was only in charge of the Mangling Machine, or anything between the two. (Like the Android managing operations on Vorticon VI only, while Mortimer controlled larger operations.) However, the most likely explanation is that the Android was just left there for Keen to find, while Mortimer was the one that did everything else.