Plot hole: In the pilot, it is established that the surface of anything/anyone made invisible by "quicksilver" is freezing. (Darien gets caught in the women's shower because the mist freezes on him. He freezes the beer mugs for the doctors.) But in later episodes, nobody notices him standing invisible - and freezing!? - next to them.
Continuity mistake: The establishing shot of the Agency's headquarters building zooms in on 3 tall, narrow windows recessed into a brick wall. We then cut to an interior view - of several wide, continuous windows without any recesses. They don't match the exterior windows at all. (00:07:30)
Albert Eberts: Great news, Robert. I was able to pull a few strings and managed to get you your very own staple remover.
Robert Hobbes: That's great. You know, I'm a highly trained, decorated field agent, Eberts. I could kill a man right now with my bare hands.
Albert Eberts: But can you collate?
Trivia: A number of in-joke Dr. Who references crop up throughout the series pilot. A group of doctors and scientists are introduced as Hartnell, Troughton, and Baker; there's a business card for I. M. Foreman in Totters Lane; and the cover of a science magazine sports headlines such as "Time and Relative Dimension in Space" and "Playing the Game of Rassilon."