Continuity mistake: In the opening scenes, Number 6 steps onto the elevator with a beard, but arrives on the lower level clean-shaven.
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 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.
Revealing mistake: The ultra-secret location of The Village is accidentally revealed when Number 6 drinks his tea. While everything in The Village is supposed to bear only its penny farthing logo, the bottom of the tea cup is emblazoned "Portmeirion Pottery." "The Prisoner" was filmed in the Welsh resort village of Portmeirion.
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 the Village doctors and technicians begin their procedure on the unconscious Number 6, one man folds the sheet and blanket back from his chest. A few shots later, the same man does this again.
Do Not Forsake Me Oh My Darling - S1-E13
Continuity mistake: Driving his Lotus through London, Number 6 passes a hearse. But when the shot cuts to a wider angle, the hearse disappears.
Continuity mistake: While the technicians are prepping the unconscious Number 6, there's no watch on the lamp table by the bed. One appears there, though, when the tech begins collecting the prisoner's personal items.
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.
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)
The Girl Who Was Death - S1-E15
Continuity mistake: In the interior shot of Number 6 exiting the lighthouse, the red doors are open. When the shot cuts to an exterior view of him coming out, the doors are closed and he opens them again.
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.
Continuity mistake: When Number 6 and Nadia get into the shipping crate, they're both able to stretch out completely for the 12-hour trip. But when the crate is opened, it's suddenly several inches shorter, and 6 has to bend his neck at an uncomfortably sharp angle to fit into it.
Continuity mistake: While he's making his graduation speech and demanding to know why Number 6 resigned, Number 2 has a mortarboard tassel wardrobe malfunction: it keeps changing sides between shots.
Visible crew/equipment: When Number 6 holds up the radio, the camera angle tilts just enough to show us a brief glimpse of the top edge of the studio set.
Free for All - S1-E4
Continuity mistake: During the campaign, watch the bass drummer as he turns left. The same taxi with the same driver passes him twice in quick succession - going in the same direction.
A. B. and C. - S1-E3
Continuity mistake: Number 6 substitutes clear water for the red-tinted drug in the syringe. But when Number 14 later injects him with the same syringe, the fluid in it has turned red again.
Continuity mistake: The judge has two glasses in front of him on the bar. When the shot changes, there's just one glass.
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.
Continuity mistake: In the saloon, between close-ups and cutting back to the master shot, the glasses in front of the men at the bar change positions repeatedly.
Chosen answer: We were never told. In the series finale [Spoiler alert] Number 6 demands an answer to that question, only to be shown his own reflection.
Jean G