 The first episode, "Why Spy?", featured cameo appearances by several  actors who had played spies in other TV shows: Lupus, Peter (qv)  ("Mission Impossible" (1966)), Macnee, Patrick (qv)  (_"Avengers, The" (1961)_ (qv)), and Culp, Robert (qv)  (_"I Spy" (1965)_ (qv)). They may or may not have been playing the  same characters as in their original series.