Here's a picture of Steven Moffat at the Paley Center for Media on Monday night. See that grim bald guy against the door in the background? I think he was museum security. During the Q&A segment of the evening, he stood vigilant at the front of the auditorium, glaring at us; keeping a baleful eye on the audience to make sure we didn't take pictures in there.
If this was Earth Prime-Time rather than Earth Prime, I would not be surprised to find out that he was an alien or some kind of cyborg sentry.
He's probably only assuming human form. His real body probably resembles the unbuttered half of an English muffin!
But of course, it would be crazy to think that way. Heh heh... heh heh.... ahem!