Premiering in the Fall of 1964 as TV's response to the popularity of the James Bond movies in theaters, THE MAN FROM U.N.C.L.E. was the story of a top American secret agent with the unlikely name of Napoleon Solo. In fact, the original pilot was just entitled SOLO. The name itself was more or less created by Bond creator Ian Fleming and, in fact, a "Solo" appears as a minor character in '64's GOLDFINGER.
The initial black and white season of U.N.C.L.E. presented some fairly serious spy stories but as color came in the following year, the series took a turn for the camp, with some episodes worse than others. Essentially, week after week, the good guys of U.N.C.L.E. (Sam?) fought to stop various plots by the bad guys of T.H.R.U.S.H.
Robert Vaughn, who had made a hit in THE MAGNIFICENT SEVEN, was cast as the star. Unfortunately for him, this became one of those series with a breakout character who usurped all the fan mail. In this case it was English actor David McCallum as Russian U.N.C.L.E. agent Ilya Kuryakin. His minor role became a major co-starring character who was, in fact, sometimes the lead in some scripts.
The pair worked well together with great chemistry and both were equally merchandised and exploited in books, magazines, toys, games and record albums.
The series was popular enough that quite a few feature films were released to theaters featuring the TV spies. These were actually re-edited versions of two-part episodes and were released mainly overseas, then syndicated back to US TV.
Two seasons in, there was even a spin-off series, THE GIRL FROM U.N.C.L.E., offering the first major role to actress Stefanie Powers. Rex Harrison's son Noel played her sidekick Mark Slate. Although it, to an extent, ripped off the classic UK comic strip MODESTY BLAISE, GIRL, premiering at the height of Batmania in 1966, was played mostly for camp.
Writer Michael Avallone made a career out of hacking out surprisingly good TV series adaptations including the MAN FROM U.N.C.L.E. and, seen here, it's spin-off.
Both MAN and GIRL had successful if unspectacular comic book runs from Gold Key, a company that ran mostly licensed projects in the sixties.
Veteran actor Leo G. Carroll (later immortalized in the ROCKY HORROR theme song) crossed over in both series as U.N.C.L.E. head Alexander Waverly.
Stefanie's April Dancer character wasn't mentioned, if I recall, in THE FIFTEEN YEARS LATER AFFAIR, a 1980's reunion movie for television that proved one of the better of its type.