Robert Vaughn worked on his Ph.D. during the course of the series and often was allowed to leave the set early so that he could attend night classes.

Ian Fleming was reportedly one of the consultants when this series was being planned. The name Solo was borrowed, apparently with his blessing, from the novel Goldfinger.

U.N.C.L.E. stands for "United Network Command for Law and Enforcement"

The show's third season saw a change of style that resulted in the amount of comedy being increased in response to the "camp" craze made popular by Batman (1966) and Get Smart (1965). As a result, UNCLE's ratings plummeted and the series never recovered. Despite a return to serious stories the next year, it was cancelled midway through its fourth season.

The stunts were usually done by actors David McCallum and Robert Vaughn as well as by stuntmen, and the best version was used. McCallum wasn't too keen on heights and Vaughan wasn't too keen on water - so they tried to avoid those stunts.

Originally, Will Kuluva was to play the head of U.N.C.L.E but was replaced by Leo G. Carroll. After the pilot was screened for the network executives, they told the producers to "get rid of the foreign guy". They really meant for David McCallum's Russian agent to get the axe, but the producers thought they meant Kuluva.

The meaning of the acronym THRUSH was never spelled out in the series, though a meaning was created for one of the UNCLE novels published at the time ("Technological Hierarchy for the Removal of Undesirables and the Subjugation of Humanity").

Access to U.N.C.L.E. headquarters was made through Del Floria's, a tailor's shop. Additional entrances were mentioned but not seen.

Every two-part episode of this series was reedited into a series of theatrical films which were initially released in Europe, and later to American TV. In each case, additional footage was shot. Among the films in this series: To Trap a Spy (1964); The Spy with My Face (1965); One Spy Too Many (1966); One of Our Spies Is Missing (1966); The Spy in the Green Hat (1967); The Karate Killers (1967); The Helicopter Spies (1968); How to Steal the World (1968).

Except for "Alexander the Greater Affair, episodes were always titled "The (insert episode title) Affair", while each act also carried its own title, usually taken from a line of dialog.

Napoleon Solo was originally to have been a Canadian. Although Ian Fleming assisted in the creation of the series, at one point EON Productions - which owned the rights to Fleming's novel "Goldfinger" - threatened legal action over the use of the name Napoleon Solo.

In the original, unaired version of the pilot episode (shot in color), the Head of U.N.C.L.E. was called Mr. Allison, played by Will Kuluva. When the program finally aired it was shown entirely in black and white with Kulava's scenes re-shot, featuring Leo G. Carroll as Mr. Waverly.

The name Illya Kuryakin comes from a Broadway play written and directed by Jules Dassin. "Ilya Darling" is Dassin's musical adaptation of his earlier film "Never on Sunday," or in Greek "Pote tin Kyriaki". The irony lies in the fact that the Kuryakin character is Russian and Dassin was blacklisted for years as a suspected Communist.

This series was a veritable hotbed for up and coming, fresh-faced TV stars just starting their acting careers. The most notable ones worth looking for are: Jack Lord, Ricardo Montalban, Sonny and Cher, William Shatner AND Leonard Nimoy (in the same episode - "The Project Strigas Affair"), James Doohan, Werner Klemperer, June Lockhart and Robert Culp. Within a few years of their guest appearance on The Man From U.N.C.L.E., they would go on to star in their own iconic TV shows from this era.

When they were filming a reunion movie, both lead actors were asked how the success of this show affected their careers. David McCallum said that he was often typecast and found it difficult to play other types of roles, Robert Vaughn said in his case the opposite was true, he played nothing but villains after the series ended.

The show was originally to have been called "Solo", but in the year it was due to come out the movie Goldfinger (1964) was released with a villain called "Solo."

At one point, the producers considered combining the show with The Girl from U.N.C.L.E. (1966) to make a single, two-hour series called "The U.N.C.L.E. Show".

The first frame of the scene change 'swish pan' showing the name "Fritz Weaver" set against London's Tower Bridge is a frame from the credits of the unaired pilot 'Solo.'

In the book, Son of Origins, Marvel Comics editor Stan Lee revealed that the Man From UNCLE TV series was the inspiration for Nick Fury, Agent of SHIELD. The comic would inspire the inclusion of the character and agency in the Marvel movies, which led to the Agents of SHIELD tv series, nearly 50 years after UNCLE premiered.

UNCLE agents and baddies used MP 40 submachine guns in episodes. UNCLE had pistols since Season 1.

The "Uncle Issue guns" were actually Walther P-38 9mm Semi-automatics. The P-38 featured a number of attachments including a scope, a barrel extension with a silencer and bi-pod and a rifle stock. These, combined with the special sound effect used when fired, gave the weapons a rather exotic mystique. A toy version was issued that included all the attachments as well as the signature triangular ID badge and an ID card. Decades later, the "Transformers" toyline featured a chrome P-38 with all attachments as the main bad guy, "Megatron".

THRUSH is an acronym for "technological hierarchy for the removal of undesirables and the subjugation of humanity".