Continuity mistake: In the beginning, the cards and notebook on Number 6's kitchen counter change positions between shots. There's also a circle card on the counter that disappears when he draws the star card from the deck.
Continuity mistake: When Alison and Number 6 are experimenting with the ESP cards, the number of cards in his hand and the designs on them changes between takes.
Continuity mistake: When the lamp begins spying on him, Number 6's bed sheets and blanket rearrange themselves from messy to neatly tucked in between shots.
Continuity mistake: Alison is thanking Number 6 for letting her practice on him. In close-ups, her hands are at her sides. But in longer shots, she has her hands folded under her chin.
Revealing mistake: In the aerial shot from the helicopter as it overflies the Village, another "real world" car can be spotted parked next to the Green Dome.
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.
Revealing mistake: Watch Curtis' shadow when he and Number 6 have their pistol range competition. The split-screen process cuts his shadow in half.
Revealing mistake: While they ride toward the helicopter, Number 6 and Number 2 have a conversation. Shots of Number 6 are obviously outdoors under windy conditions: his hair is blowing. But every shot of Number 2 has been taken in-studio with a rear-screen projection. His hair isn't moving at all.
Continuity mistake: Watch the helicopter when it first lifts off. It has regular "sled-style" landing struts. But in the air, it suddenly has water pontoons. When it lands again, though, the regular struts return.
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.
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.
Visible crew/equipment: After uncovering the deception Number 6 enters his doppelgängers home to confront him. As the door opens you can see the shadow of a crew member on the wall next to the door. He is hidden behind the partition. (00:39:18)
Revealing mistake: When Alison enters Number 2's chamber we see a POV shot of Number 6, Number 2 and the doppelgänger facing the camera. If you look closely you can see jittery lines at various points on the screen were the two Number 6's have been poorly overlaid. (00:26:24)
Revealing mistake: Throughout the shooting competition between Number 6 and his Dopplegänger there are numerous shots where both Number 6's are facing the camera and you can see a jittery line running down the middle of the shot where the shots were poorly overlaid.
Revealing mistake: When Number 6 lights up a cigar with the other Number 6 you can see by watching the cigar smoke that there is an exact point on the screen where the cigar smoke cannot travel beyond, revealing that there are two shots being overlaid. (00:16:41)
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