Factual error: The truck transporting Number 6 and Nadia drives on the left side of the road. Fine for England, where the scene was shot - but they're supposed to be in Poland, where everyone drives on the right.
Factual error: Alison's Polaroid pictures develop themselves instantly. (In reality, you had to wait just over a minute before separating the developer sheet and finished photograph.) She also leaves the same flash bulb in when she takes a second picture - and it flashes again.
The General - S1-E6
Factual error: When Number 6 types "WHY?" on the typewriter, the sheet of paper comes out with the word centered on the page. But the typewriter's carriage was pushed all the way to one end, so the word couldn't possibly have wound up in the page center.
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.
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.
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