Continuity mistake: The telephone kiosk Number 6 uses at the beginning changes both its shape and its location between takes. Sometimes it's under an archway: in other shots, it's next to the restaurant instead. And in some shots, the hood above the phone has square/straight edges, while in others, its edges are round.
Free for All - S1-E4
Continuity mistake: While Number 6 and the maid are in the kitchen, the toast rack moves itself several feet in between takes. It's on Number 6's right, then suddenly appears on his left instead.
Continuity mistake: When No.2 is writing on the blackboard, in Question A. The capital letter "F" changes several times between the long shots and close ups. Also in Question B. The position of the first "T" in the word together also shifts position during the same shots, showing that the scene was filmed twice.
Continuity mistake: When Number 6 is looking for a map in the Village store, the shopkeeper wears a badge with 19 on it. A few shots later, his number has mysteriously changed itself to 56.
Free for All - S1-E4
Continuity mistake: The sequences of Number 6's campaign speech scene were apparently filmed several months apart from each other. The trees behind him change from Springtime bloom to Winter bare and back again continually.
Do Not Forsake Me Oh My Darling - S1-E13
Continuity mistake: When Seltzman is talking to Number 2, there's a chair beside the tea cart with a foot rest, visible in the shots from behind Number 2. But when the camera angle changes to Seltzman's POV, the same chair appears in the shot - without its foot rest.
A. B. and C. - S1-E3
Continuity mistake: During the dance, the bottle of wine on Number 6's table is sitting on the left side. No one touches it, but when he and B come back to the table, the wine has moved itself to the center.
Continuity mistake: Number 6 is looking out his window as the maid runs down the stairs. As he watches her, two tables in his apartment change places with each other between takes. A large table with a statue/sculpture on it switches positions with a smaller table on which his lamp and telephone rest.
Continuity mistake: When Number 6 climbs to the top of the bell tower and looks down at the Village, the beach below him changes remarkably between shots. The sequence was obviously shot at different times of day, as the tide is in during much of the scene, but in several intervening shots, the beach sand is completely exposed.
Continuity mistake: Watch the Butler standing in the background after the committee exits the meeting room. A very bad edit causes him to jump to a different position (a foot further away than he was before) between shots.
Continuity mistake: The new supervisor holds a clipboard in both hands up near his chest. When the shot cuts, he's abruptly holding it in one hand down at his thigh.
Continuity mistake: At the start of the chess match, a man holding a stick climbs the ladder behind the Queen and settles in to watch. As Number 6 and the Queen converse throughout the game, however, both the ladder and the man have vanished. They both reappear behind the Queen as the game is ending.
Continuity mistake: When Number 6 observes the stone boat, the tide appears to change from high to low between shots.
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: At the end, Number 6 and the Butler catch a bus near Westminster Bridge in London. The bus that drives up and stops for them has no back platform. But when they board, the style of bus suddenly changes to the more common type with an entrance in the back.
The General - S1-E6
Continuity mistake: At the end, the Professor and Number 12 fall dead on the ramp. Between shots, their positions change.
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.
The General - S1-E6
Continuity mistake: Number 6 is stabbed in the hand during his struggle with the projectionist. After he's treated for the injury, not only is he placed in an unnecessary sling (his arm wasn't broken), he's also suddenly bleeding from the forearm, several inches above the area where he was stabbed.
Free for All - S1-E4
Continuity mistake: Number 6's bed tidies itself in the scene where the spying lamp is lowered from the ceiling. First the bedcovers are rumpled and disarrayed. Then in the next shot, all is straight with the blanket neatly folded at the foot.
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.
Answer: It's even more obvious than you think, you know who number 1 is in the very first episode. When 2 replies to the question "who is #1?" Change the way he answers from you are number one (in the monotone or accented answer to, "You are, number 6. The comma gives you the answer. #6 is #1. It's the tone of the answer.