[SPOILERS] SOMA unsolved mysteries thread

[Abion47]

There was definitely the other guy in that room getting attacked by the Construct. However, I don't see it as very likely that he was another Simon-like Mockingbird. For one, there is only the one Pilot Seat in Upsilon, and Simon himself is occupying it. For another, a humanoid Mockingbird requires a human body as a host, and all the humans from Upsilon are accounted for.

But even if he was a humanoid Mockingbird, that still doesn't explain what he was doing there. Like I said, everyone from Upsilon was accounted for, and Upsilon itself was in a state of lockdown. No one else from the entirety of Pathos-II had any reason to go anywhere near Upsilon. (Imogen Reed is the one exception, but her body was used for Simon.)