Audio problem: Number 48 is still singing when he's carried out near the end - his lips are moving but we don't hear anything. A few shots later, we can hear him again, but his lips aren't moving in sync with the sound.
Continuity mistake: At the end, Number 6 and the Butler catch a bus near Westminster Bridge in London. The bus that drives up and stops for them has no back platform. But when they board, the style of bus suddenly changes to the more common type with an entrance in the back.
Visible crew/equipment: Number 6 enters the room with the huge globe, and we "follow" him around a map table. As the camera passes the table, it films its own shadow falling across the map.
Visible crew/equipment: When Number 48 jumps from the council table, there's a clear shadow on the left of someone holding up a still camera.
Continuity mistake: In the final scenes, as helicopters are taking off from the Village, the bell tower that's always been there is visible in some shots, but in others, it has disappeared.
Continuity mistake: The council members' signs keep changing during the "Dem Bones" sequence. "Entertainment" becomes "Anarchists" and several others switch places between cuts.
Continuity mistake: In the opening scenes, Number 6 steps onto the elevator with a beard, but arrives on the lower level clean-shaven.
Chosen answer: We're led to believe Rover is some kind of robot in the series. According to books on the show, Patrick McGoohan was looking for an unusual guardian for the Village, looked up at the sky, and saw a weather balloon, which was what Rover was.
Captain Defenestrator