Continuity mistake: At the end of the chess match, the player wearing blue comes down off his platform, descending the ladder and walking onto the field. In the very next shot, as his opponent approaches Number 6, the man in blue is in the background, once again coming down the same ladder. He didn't have time to climb it again.
Continuity mistake: In the opening shots, the Village center is shown without the giant chessboard set up. In the very next shot, it is suddenly fully laid out on the green.
Continuity mistake: When the command "Knight to Queen's Bishop Three" is given, it's not a knight that moves, but a pawn. In the next long shot, though, Queen's Bishop Three isn't occupied by anyone, pawn or otherwise.
Factual error: Several of the chess moves called out over the loudspeaker are not possible with the players in their current positions. The Queen, for instance, is ordered to King three while in her starting position (can't be done). The "Knight to Knight's Bishop three" move is also impossible. When she is free to move to King three, though, the Queen goes there twice - without moving anywhere else in between.
Continuity mistake: When Number 6 is setting up his antenna, there's a woman on the beach in the background in a blue bathing suit. Between takes, her beach umbrella disappears.
Visible crew/equipment: When Number 6 is listening to classical music in the listening booth, each time he puts his head into the booth (after switching records) there is a specific shot behind his shoulder where you can see the heads of two crew members reflected in the glass of the listening booth. This happens 3 times and is very visible on Blu-ray. (00:10:33)
Revealing mistake: After Number 14 convinces Number 2 to let him deal with Number 6 both of them leave 2's office. As they do, you can see the "metal" on the doorframe has started to bubble. (00:30:57)
Continuity mistake: When Number 6 writes the coded message he uses black ink, after Number 2 intercepts the message it changes to blue ink. (00:37:24 - 00:38:30)
Continuity mistake: When Number 2 is shouting at Number 14, calling him a traitor, Number 2's long strands of hair are flying all over his head. In the very next shot, though, his hair has nicely combed itself and he's well-groomed again.
Continuity mistake: The new supervisor holds a clipboard in both hands up near his chest. When the shot cuts, he's abruptly holding it in one hand down at his thigh.
Continuity mistake: Number 6 points the mirror out to sea and tries to send a signal. But when we see him from the POV of the security camera, he's pointing the signal mirror toward the Village instead. When the shot cuts back to him on the beach, the buildings are again behind him and he's facing seaward again.
Continuity mistake: During their kosho match, Number 6 ends up dangling Number 14 over the water. In the first shot, he's holding the man with his left hand. In the next, he's using his right hand.
Continuity mistake: Just before the fight begins on the roadway, Number 6, in full shot, steps off the grass and onto the road. But the next close-up of him shows him on the grass again.
Continuity mistake: Between the time the coded note is tied to the pigeon and the time it is intercepted and handed to Number 2, the handwriting on it changes completely.
Continuity mistake: When he's standing against the wall of the kosho chamber, Number 6 is holding onto the rail, but when the camera reverses angles, he isn't. This goes back and forth several times.
Continuity mistake: During Number 6's visit to the Village Shop, the blue and yellow signs in the window switch places between takes, then return to their original positions.
Continuity mistake: Number 6 recites a classified ad in Spanish to the young woman at the newstand. His phrase contains eight words, but when she reads them back, there are nine.
Revealing mistake: Obvious stunt double for Patrick McGoohan in some shots during his exercise routine. (00:11:53)
Audio problem: During the scene when Number 6 warns Number 2 of a potential assassination attempt on him Number 2 brushes it off and says "it's the little watchmaker that concerns you" but his mouth does not match this. (00:29:43)
Visible crew/equipment: Just before Number 6 and the woman break into her father's watch shop there is a shot of the shop's front door, as the camera moves in on the door you can see the face of the cameraman reflected in the door glass in the bottom right. (00:32:01)
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