Visible crew/equipment: In Number 2's chamber Number 6 refuses his offer and says "You won't hold me" as he turns around and goes to walk out. If you look at the bottom right of the screen you can see the shadow of the boom microphone cast on the floor. (00:15:20)
Visible crew/equipment: In the foot-chase-on-the-beach scene, there are tracks in the sand from the camera crew's truck. They vanish and then reappear when the camera angle changes.
Visible crew/equipment: As Number 6 storms out of Number 2's chamber, the camera dolly is briefly visible moving out of his way at the lower left of the screen.
Visible crew/equipment: When Number 6 first walks into his Village bedroom, a film crew member can be spotted walking past the window.
Visible crew/equipment: Watch the bottom left corner of the screen when Rover turns around and begins pushing Number 6 away from the helicopter. A film crewmember's head (probably that of the technician operating the weather balloon that played Rover) appears briefly in the shot.
Visible crew/equipment: When Number 6 holds up the radio, the camera angle tilts just enough to show us a brief glimpse of the top edge of the studio set.
Answer: It's even more obvious than you think, you know who number 1 is in the very first episode. When 2 replies to the question "who is #1?" Change the way he answers from you are number one (in the monotone or accented answer to, "You are, number 6. The comma gives you the answer. #6 is #1. It's the tone of the answer.