The Prisoner was filmed in the North Wales resort village of Portmeirion over the course of a year. Patrick McGoohan was inspired to film his series there after filming a couple of Danger Man episodes in the village.

McGoohan arranged for another actor to play Number Six for one episode (a mind-swap story) so he could take time off to film Ice Station Zebra.

Patrick McGoohan would have liked to limit the program to seven episodes, but there was no chance that ITC executive Sir Lew (later Lord) Grade would back such a short run, so he reluctantly agreed to make two "series" of thirteen each. The first was to end with "Degree Absolute" (later retitled "Once Upon A Time," when it was decided to make it the first half of a two-part finale). When the point in time came when the entire run was supposed to be in the can and only the first thirteen episodes actually were, Grade pulled the plug (or, according to some, McGoohan told him that the premise wouldn't yield another thirteen stories). Eventually, Grade was convinced to allow four more episodes to be made, including a finale, but with the proviso that production continue uninterrupted. Many of the crew were committed to other projects (script editor George Markstein's departure is attributed to a falling out with McGoohan, but as he left at the exact same time as all the others, this is debatable), including McGoohan himself, who co-starred in the Hollywood movie, "Ice Station Zebra" (1968). For filming to be able to continue in his absence, "Do Not Forsake Me, Oh My Darling," with The Prisoner's mind transferred to another man's body, was concocted, and replacements for departed crew members were found. After the star returned from America, shot his ending speech and a few insert shots for "Darling," and the episodes "Living In Harmony" and "The Girl Who Was Death," he then confessed to Grade that he had no ideas for the finish (he knew only that he wanted no conventional "James Bond" type finale, such as one suggestion, allegedly from Markstein before he quit, that Number One turn out to be The Butler). Grade replied that the actor was obligated to come up with something. McGoohan locked himself away for most of the next week and wrote, "Fall Out" while the two episodes from the abandoned final season of "Danger Man" ("Koroshi" and "Shinda Shima," later reedited into a feature film, Koroshi) preempted "The Prisoner" for two weeks to buy him the needed time. Actor Kenneth Griffith, who plays The President in the final episode, has repeatedly claimed that he was asked to write his own speech (singular his). As the character talks only in speeches, this is less than clear, but at least Griffith specified that his point was how pressed for time McGoohan was.

"Rover", the menacing white balloon that acts as a surreal sentry in The Village, was supposed to have been a large robotic machine. During the filming of the first episode, it was supposed to travel across water on a pair of rails hidden under the surface. The machine fell off the rails and into the water, damaging the motors inside. Just then, a weather balloon passed by, and McGoohan came upon the idea of "Rover" being a large white balloon that traveled by itself. The reason the cast stands still as Rover wanders past is because the balloon is being pulled by a wire. The shots were then run backwards, and edited into the film (In one episode, smoke can be seen drifting back into a chimney in the distance as Rover passes by).

It has been speculated that Number Six is in fact John Drake from McGoohan's earlier series, Danger Man. Several references to the earlier series appear, and some believe he is referred to by name in one episode (though others interpret the dialogue differently). Officially sanctioned novels based on the series refer to Number Six as John Drake.

The episode "The Girl Who Was Death" was originally written for Danger Man.

According to some published sources, McGoohan received very little notice that the series was to come to an end. He reportedly received word as filming concluded on the episode "The Girl Who Was Death" and he was given a short deadline to come up with a finale episode.

Patrick McGoohan was adamant that Number Six not become romantically involved with anyone on the series (carrying over a policy he put in place for his John Drake character in "Danger Man"). Nonetheless, writers tried to pair Number Six up with female leads on a few occasions, only to have their efforts vetoed by McGoohan. The characters played by Nadia Gray in "Chimes of Big Ben" and Angela Browne in "A Change of Mind" were both written as love interests for Number Six, and there was reportedly a bed scene written for "Chimes" but McGoohan would have none of it. The closest Number Six comes to romance is in his friendship/sympatico with Alison in "The Schizoid Man" and in the character of an observer who falls in love with him in "Dance of the Dead."

Interiors were shot in a studio located next door to the studio used for filming 2001: A Space Odyssey. A special effects shot of a starry sky that was created for the movie was borrowed by the producers of the TV series for use as an insert in an early edit of the episode "Chimes of Big Ben". Though cut from the televised version, the early edit of the episode including the 2001 footage was later released on video and DVD. (The starry night shot appears in the sequence where No. 6 uses a handmade device to study the sky in hopes of determining The Village's location).

The episode "The Girl Who Was Death" was originally conceived as a two-part story.

Star and creator Patrick McGoohan planned to produce a movie remake in 2002, but plans were shelved.

Ron Grainer's theme music was titled "The Age of Elegance" and according to some sources predates "The Prisoner" by several years. However, many sources claim that the theme music is yet another creation of Patrick McGoohan himself. Reportedly, he whistled it into a tape recorder, Grainier transcribed that onto sheet music, did the arrangements and orchestrations and deserves credit for getting the music into good shape.

Patrick McGoohan and "Number 6" were both born on the same day, 19 March 1928 according to the episode Arrival.

The final two episodes, "Once Upon a Time" and "Fall Out", were filmed a year apart due to the decision to extend the series and a shaving scene had to be written into the latter episode to explain actor Leo McKern's change of appearance.

Unusually for a 1960s TV series, two episodes were broadcast without opening credits sequences: "Living in Harmony" and "Fall Out."

There is much debate over the proper order in which the episodes should be viewed, as neither ITV in Britain nor CBS in the US originally broadcast the episodes in production order. The A&E DVD release in 2001 placed the episodes in what it described as the "fan-preferred" order (though this is open for debate). The episode viewing order suggested by A&E is as follows:

1. Arrival

2. Free for All

3. Dance of the Dead

4. Checkmate

5. Chimes of Big Ben

6. A, B and C

7. The General

8. The Schizoid Man

9. Many Happy Returns

10. It's Your Funeral

11. A Change of Mind

12. Hammer Into Anvil

13. Do Not Forsake Me Oh My Darling

14. Living in Harmony

15. The Girl Who Was Death

16. Once Upon a Time

17. Fall Out

The series first aired on American TV in 1968 as a summer replacement for a 'Gleason, Jackie' series.

The rough cut of the first episode, "Arrival", was reportedly more than two hours long.

The building in Portmeirion shown as Number Six's house in the series became a gift shop selling Prisoner-related merchandise.

CBS refused to broadcast the unusual episode "Living in Harmony," stating that its depiction of the use of mind-controlling drugs was inappropriate, though the network did broadcast other episodes with similar plots, most notably "A, B and C".

According to script editor and co-creator George Markstein, Number Six resigned from his position after discovering files indicating the existence of the Village. The Village was an idea Number Six had submitted to his superiors many years before but had since decided was monstrously inhuman.

The bald-headed man sitting behind the desk during the opening credits was George Markstein, script editor and co-creator of the series.

Among the musicians who worked on The Prisoner theme is guitarist Vic Flick, who also played the famous James Bond Theme in the early 007 movies.

Only two actors played Number Two more than once: Leo McKern in "Chimes of Big Ben," "Once Upon a Time" and "Fall Out"; and Colin Gordon in "The General" and "A, B and C." Several other actors who played Number Two also appeared in other roles in the series (e.g. Kenneth Griffith as No. 2 in "Girl Who Was Death" and as The Judge in "Fall Out.").

On several occasions since the 1970s, plans have been made to adapt The Prisoner into a motion picture. McGoohan once considered filming a sequel that took place 100 years or more after the TV series. The most recent attempt at a remake was announced in 2001 with McGoohan as executive producer and directed by Simon West.

Both Brian Cox , and Sir Clough Williams Ellis - creator of Portmeirion - worked on the series as extras.

Patrick McGoohan vehemently denies that Number Six is John Drake.

McGoohan also starred in an earlier TV film entitled The Prisoner (1963) (TV), which, while unrelated to this TV series, shared more than a few similarities with it.

Co-creator George Markstein later wrote a book about a real-life facility similiar to (but nowhere near as sinister as) The Village which was reportedly set up in a remote area of Britain during WWII in order to protect people with knowledge of sensitive information.

Ranked #7 in TV Guide's list of the "25 Top Cult Shows Ever!" (30 May 2004 issue).

The series' enigmatic finale was so controversial that, according to legend, Patrick McGoohan had to go into hiding for a time.

In order to create their characteristic movement, the Rovers were filled with a mixture of air, helium and water.

In some shots, a pursuing Rover was managed by connecting it by wires to the feet of its "victim".

The 1967 world television premiere of the series was actually in Canada (on the Canadian Broadcasting Corporation-CBC) - shortly before the UK airing.

The initial letters of the key episode "Chimes of Big Ben" spell out "COBB", the name of a key betrayer of Number 6 from the episode "Arrival".

While most Number Twos are male, during the course of the series we see at least four women in the position ("Dance of the Dead", "Free for All", "Many Happy Returns" and a female Number Two is seen very briefly in "It's Your Funeral").

In the episode "Many Happy Returns", the Prisoner's former London residence bears just a single number on its door: 1.

Revealing mistake: It was not always possible to mask the existence of civilization near Portmeirion, Wales, where much of the series was filmed. In several episodes neighboring towns and farms can be glimpsed, and in "Many Happy Returns", low-tide reveals No. 6 could have easily escaped by walking across the bay. However, it should be noted the exact size of The Village is never specifically indicated, and there are numerous episodes that indicate it is significantly larger than the core townsite.

Continuity error: In the episode "Once Upon a Time": the handwriting on the blackboard significantly changes between shots (i.e. it is noticeably different handwriting in one shot, then another). This is most noticeable during the sequence where Number Two writes "BANG!" in close-up and then points at Number Six; the writing changes between shots.

Revealing mistake: In the episode, "A Change Of Mind", No. 6 is walking along a path after leaving a meeting with The Council. He comes across another inmate and says, "Beautiful day, number sixty one." The inmate, a woman, ignores him and moves on. No. 6 continues walking up the path, and a few seconds later, you can see a white four-door British sedan pass by the gate at the top of screen, directly in line with the end of the path. Tourist passing through, no doubt: all the vehicles in The Village are Mini Moke taxis.

Continuity error: In the episode "Free For All", during Number 6's attempted motorboat escape, the enforcer attacks and knocks him off the boat with a long steel rod. When the goon lifts the rod over his head to bludgeon No.6 (who is hanging off the side of the boat) with it, Number 2 shouts from the helicopter above, "Don't do anything rash! Give him time." With him momentarily distracted, No. 6 reaches up and pulls the henchman into the water - in this shot the steel rod has vanished completely.

The closing credits of all but one episode end with footage of "Rover" (the big white balloon) emerging from the sea. The final episode, "Fall Out," omits this footage. The credits of the "alternate" version of "Chimes of Big Ben" don't use this footage either; instead, they end with a crudely animated earth exploding as the word POP fills the screen.

The episode "Living in Harmony" does not have opening credits and the series title "The Prisoner" never appears on screen. The episode "Fall Out" also does not have an opening credits sequence, replacing it with a recap of the episode "Once Upon a Time." The series title does appear on-screen, however.

Patrick McGoohan does not receive on-screen acting credit on the final episode "Fall Out." His on-screen credit simply reads "Prisoner."

The only episode to feature a pre-credits sequence is "Do Not Forsake Me Oh My Darling."

In the two episodes in which Alexis Kanner receives screen credit ("Living in Harmony" and "Fall Out") his name is surrounded by a white box. No other actor's name is emphasized in this way.

The episode "Fall Out" begins with a special dedication to Sir Clough Williams-Ellis, acknowledging him and the Hotel Portmeirion on screen before the title "Fall Out" appears.

Most (but not all) episodes begin with a recap taken from the first episode of Number Six waking in his "new home" and looking out of his window at the Village. This is followed by a standard dialogue between him and Number Two (i.e. "Where am I?" "In the Village.") which plays out under the episode credits. In most episodes, the actor playing Number Two recites the lines during this sequence, but in some episodes an uncredited male actor does the chore. The sequence is altered on two notable occasions: The Number Two played by Colin Gordon in two episodes introduces himself as "I am Number Two" instead of "The New Number Two" as all other actors do. In the episode "Many Happy Returns" the face of that week's Number Two is not revealed during the sequence in order to preserve the element of surprise.

Portmeirion, Wales is not identified as the location for filming in all but the final episode. Instead the closing credits in these episodes simply say "Filmed on location."

An alternative version of "Chimes of Big Ben", the second episode to be broadcast, is available on video. Besides different closing credits, the opening credit sequence features different music as well. In addition, several scenes that were never aired appear in this version, including one that indicates No. 6 has already located the Village, not only rendering the rest of the episode moot, but also much of the series!

British video releases of the series in the early 1980s edited episodes together into several 2-hour "movies." Some of these have been televised.

CBS Television Network in the United States refused to carry the episode "Living in Harmony", supposedly due to its anti-war message (the hero refuses to carry a gun). At the time CBS claimed their rejection was due to the use of hallucinogenic drugs in the plot. While many prefer the anti-Vietnam scenario over the drug theory, several facts support CBS' version. First, they had already broadcast two episodes of entertainment series that were clearly against U.S. involvement in southeast Asia ("Route 66", March 22, 1963; "Twilight Zone", Sept. 27, 1963). Secondly, the drugs in "Harmony" are quite different from those used in other "Prisoner" episodes. On most occasions, they have no more in common with recreational "junk" than truth serum as seen in more realistic spy dramas, while the plan here was to take our hero and "fill him with hallucinotory drugs....dis-orient him" according to the episode's dialogue. There is actually a third theory that is more likely than either of those. "Living In Harmony" is not identified as a segment of "The Prisoner" until the end, unless you recognize star Patrick McGoohan, the parallels to "Arrival", and the typeface used in what credits there are (the episode title appears to be the series title). When the program was first broadcast in the U.K., in some regions (it wasn't shown simultaneously across the country as in the U.S.) superimposed the words "The Prisoner" over the image at the beginning. Star/Executive Producer/Creative driving force Patrick McGoohan reportedly didn't like this at all, but it would have forewarned him to contractually prohibit CBS from doing the same thing. According to this theory, CBS declined to air the episode rather than gamble on the intelligence of their audience.

When it first aired in French, the episode title "The General" and all references in the dialogue were changed to "Le cerveau" (The Brain), presumably to avoid any reference to General De Gaulle (then the country's leader)

Alternate versions of the opening credit sequence were created for non-English speaking countries. The file-cabinet drawer ahows the word "RESIGNED" in the applicable language. Examples of this "foreign file drawer" footage were released as bonuses in the A&E DVD release.

A preliminary edit of the first episode, "Arrival", was broadcast by accident on one PBS station in the 1970s. Although the original negative of this edit has been lost, a videotape copy was discovered and released on DVD in 2002. Among the major differences from the officially broadcast version:

Different theme music and differently edited opening credits (same as the alternate version of "Chimes of Big Ben.")

Slight differences in the sequence where No. 6 wakes up in the Village for the first time.

A longer version of the sequence where No. 6 tours The Village by taxi.

When Rover is introduced, it does not kill a villager as it does in the televised version.

Longer version of the sequence where No. 6's radio-controlled helicopter returns to the Village.

Different closing credits, ending with an image of Earth and the universe turning into the pennyfarthing bicycle logo. Also, Wilfred Josephs is credited as musical director.