Continuity mistake: At the end, the computer produces a print-out with two lines of type at the bottom, then pauses. In the next shot, when it starts printing again, the two lines have disappeared.
Continuity mistake: When Number 6 falls on the beach, the sand under him is wet. In the next shot, it is obviously dry.
Continuity mistake: Number 6 pushes the dead body out into the surf. In close-ups, the body is still very near the shore. But in long shots, it is much further out. (00:28:30)
Revealing mistake: When Number 6 finds the black cat outside his house you can see his shadow fall across the painted backdrop of the town behind him. (00:11:39)
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