Continuity mistake: Monique's position on the floor reverses while she's unconscious. When she first collapses, her feet point to the corner of the room. When she comes to, her head is toward the corner. When she gets up, her feet are oriented toward the corner once again.
Continuity mistake: The towel in Number 6's locker changes colors. When we first see the locker opened, the towel is white. A few shots later, when it's opened again, the folded towel has turned blue.
Continuity mistake: The cape Monique is wearing disappears when she's in the watch shop, then reappears a few shots later.
Continuity mistake: A sleeping Number 6 is being observed by the Village girl. While she watches him, his bed clothes mysteriously rearrange themselves. First they're disarrayed, then they're neatly tucked over him and his robe has moved to a different place on the bed. A few shots later, when he wakes up, his pillow disappears.
Continuity mistake: When Number 6 buys soap and candy from one of the Village vendors, he removes his payment card from his pocket three different times without ever having put it back.
Continuity mistake: During the scene in the bell tower, watch the beach in the background. In one take, the tide is in. In the next, it is suddenly at low tide, with much more of the beach exposed.
Visible crew/equipment: At the end of the episode when Number 6 gives Number 2 the device and tells him to leave the island immediately you can see the shadow of the boom microphone on the stone wall behind them at the top right of the screen. (00:47:17)
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)
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)
Revealing mistake: Obvious stunt double for Patrick McGoohan in some shots during his exercise routine. (00:11:53)
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