The Avengers was a British TV series made by Associated British Corporation and ran for six seasons between 1961 and 1969. That came as a surprise to me, because I only remember the last two seasons. More on that later.
The one constant character in the series was John Steed, the bowler-hatted, Saville Row-suited, umbrella-carrying member of an unnamed British organization that simultaneously fights crime and deals in espionage and counter-espionage missions. Steed was played to perfection by Patrick Macnee.

Surprisingly, Steed was not the original lead character in The Avengers. That honor goes to David Keel, a physician whose fiancee was murdered. He was determined to find her killer when he crossed paths with Steed, who was after the same man for a different reason. By the end of the second episode, Keel and Steed had formed a partnership. Keel was played by Ian Hendry.

After the first season, Hendry left to go into movies (notably the Vincent Price classic Theater Of Blood) and the series was re-tooled with Steed as the lead character. His first partner was Venus Smith, a nightclub singer with no background in crime fighting or espionage. She was smitten with Steed, which was the only thing that kept them together. Venus was played by Julie Stevens.

His next companion was Mrs. Catherine Gale, an anthropologist who was an expert in judo and had a penchant for leather clothes. Cathy had been widowed in Kenya, and saw her work with Steed as service to her country. Some of the first Cathy episodes in Season 2 were originally written for Keel, and his lines (with modifications as needed) were simply given to Cathy. Cathy was played by the amazing Honor Blackman.

Cathy was unlike any other female character on British TV at the time. She was older (in her early-mid 30’s) and, because the scripts for her were originally written for Keel, was more mature and apt to argue with Steed. The attraction between the two of them became obvious, particularly in the third season, although it never got past the flirting and innuendo stage. At the end of the third season, Ms. Blackman was cast as Pussy Galore in the James Bond film Goldfinger, and left the cast.
At about the same time, the American Broadcasting Corporation in the US signed a deal with Associated British Corporation to co-produce the show, with ABC (US) airing all the new episodes. ABC (UK) agreed to shoot the new episodes on 35mm film rather than videotape, resulting in a clearer picture and better sound.
Honor Blackman’s replacement was Diana Rigg, as Mrs. Emma Peel.

The demeanor of the show changed with Mrs. Peel’s debut. Compare the theme music from the first three seasons, written by Johnny Dankworth:
with the theme music from seasons 4-6, written by Laurie Johnson:
The relationship between Steed and Mrs. Peel was more playful, the cases a little more absurd, the technology more advanced. Season 4 was shot in black and white, while seasons 5 and 6 were produced in color.
Diana Rigg left the series at the end of the fifth season. The story was that Mrs. Peel’s husband had been found in the Amazon jungle and he was brought back to England and reunited with his spouse, who then left Steed and rode off into the sunset with her husband. She was replaced almost immediately by Tara King, played by Linda Thorson. Here is that scene.
Unlike Cathy and Emma, Tara (nicknmed “ra-boom-de-ay” by Steed) was a trained (but inexperienced) agent of Steed’s organization. The flirtation between her and Steed was more pronounced, and the cases even more absurd.
I didn’t start watching the show until the fifth season, when ABC in the US ran it on Friday nights. I was twelve at the time, and while it’s unclear whether Diana Rigg in her leather catsuit brought on puberty in me, it certainly fanned the flames.
Our local religious broadcaster (who also shows reruns of Steamboat) has been running the episodes of Seasons 2 and 3 (plus the two or three episodes of Season 1 that still exist) pretty much nonstop for several years now. I seem to remember that Hollywood Video had a number of the videocassettes of those seasons on their shelves until they went out of business, and for some strange reason I believe that the station bought those VHS tapes and has been showing them nightly…
Now, for your listening pleasure, all the opens and closes for the series.This is the last of my draft picks. I hope you’ve enjoyed them!