There was a dispute over what the name of the villainous spy agency would be. The original name was THRUSH, but it was felt that this was too close to the name of the Russian spy agency SMERSH, so the studio ordered a name change for the film version. Hence, the name was replaced by "WASP" for the film version, and Robert Vaughn dubbed the word into the dialogue for all characters. The name THRUSH was used for the rest of the series, though.
In 2016, Fritz Weaver, who played the series' first THRUSH villain, died about two weeks after the death of leading man Robert Vaughn.