Mrs Peel's cover when investigating Jephcott is that she represents a firm called "Winnell and Fentle's chain stores", a reference to series producers Julian Wintle and Albert Fennell.
Steed's vintage car in the tag scene, the Beeston Humber 16/20hp, appeared in Those Magnificent Men in Their Flying Machines or How I Flew from London to Paris in 25 Hours 11 Minutes (1965) as the car belonging to the German entrant, Colonel Manfred von Holstein.
Tag scene: Mrs Peel drives off in her Lotus Elan, HNK999C, leaving Steed in his car to puzzle over a crossword.
The first appearance of The Cybernauts.
John Hollis plays the karate sensei in this story. He would later make an uncredited appearance in the pre-title sequence of For Your Eyes Only (1981) as Ernst Stavro Blofeld. Burt Kwouk (Tusamo) and Bernard Horsfall (Jephcott), as well as Diana Rigg and Patrick Macnee, would also appear in Bond films later.