Revealing mistake: On the raft, when Number 6 starts to take apart his radio, you can see that the raft is in very shallow water but it's supposed to be out at sea. (00:10:25)
Continuity mistake: When Number 6 jumps from the gunrunners' boat, he's on the starboard (right) side. In the next shot, though, the bad guy shoots at him from the boat's port (left) side. (00:20:30)
Other mistake: They search for the location of the Village by using map co-ordinates, which are checked out using a military aircraft. The Village is eventually discovered and found to be on an island somewhere in the Mediterranean sea. Number 6 is ejected from the aircraft back to the Village. However, in the final episode, i.e. 'Fall Out,' the Village is found to be in somewhere in the UK. They escape in a truck and end up traveling to London.
Factual error: Number 6 wakes up to find the Village deserted, but the central plaza fountain is still running - until he looks at it from the bell tower, when it's suddenly off. The Village fountains never appeared to be on timers (they were always on, day and night), and no one is there to turn the water off, yet it's somehow still off when Number 6 returns at the end.
Continuity mistake: While the gunrunner is untying the raft, he's holding a half-eaten green apple in one hand that wasn't there in the previous shot. It disappears again as the raft floats away. Then it comes back - but it has now become a red apple instead of a green one.
Continuity mistake: One of the bad guys prepares a tea tray in the boat's galley and carries it up to the bridge. Throughout his preparations and his trip up the stairs to the upper deck, the contents of the tray keeps changing. The items rearrange themselves, and the size and shape of the bread loaf alternates several times.
Continuity mistake: The windows in Number 6's flat are curved on the inside (as is the wall). But on the outside, the windows are flush against a flat wall.
Continuity mistake: Mrs. Butterworth has a sandwich plate in her left hand and her cigarette in her right - until the shot cuts, at which point the cigarette and the sandwiches have instantly changed to the opposite hands.
Revealing mistake: When Number 6 is fighting the two smugglers on the deck of the boat you can see creases in what is supposed to be a foggy background.
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