Dr. Warren claims he has always been unstable—"genius and madness are two sides of the same coin"—but since the geth attack, he has become almost completely unhinged, and Dr. Warren has been forced to medicate him.
Manuel blurts out comments that at the time make no sense to Commander Shepard or any of the rescue team; however, they prove to be an accurate foreshadowing of things to come. He is convinced that the age of humanity is over and there is absolutely no hope. When asked about Nihlus, Manuel claims he saw "the prophet" leading the enemy, but had in fact seen a different turian, Saren Arterius.
When Shepard asks Dr. Warren about Manuel's state of mind, the Commander has the opportunity to punch Manuel unconscious.
- Unused audio in Mass Effect 2 shows that Firewalker scientist Dr. Manuel Cayce and Manuel are the same person. As it was cut from the game it is not considered canon.
- Chris Postle, who voices Manuel, also voices several other characters in the Mass Effect franchise: Jahleed, the Normandy Requisitions Officer, and Corporal Toombs. Previously, he provided the voices for Gravedigger Shen and the Rat Demon in BioWare's Jade Empire.