One of the more popular sitcom trends in the 60's involved fantasy and/or horror. However, the average lifespan for these sitcoms was about 2 years. The Munsters & The Addams Family each lasted two, and were virtually mirror images of each other, except that Addams was adapted from a popular comic strip in The New Yorker. Each series has been revived at least once, though the Addamses have a distinct advantage, as they've also been revived in animated form twice (1973 & 1992).
The Ghost & Mrs. Muir bowed on NBC in 1968, then moved to ABC the following year, but unlike the other fantasy-coms the latter network had (Bewitched & The Flying Nun), this wasn't from Screen Gems and comedy chieftain Harry Ackerman. Instead, this came from 20th Century Fox, which had released a feature film version a few years earlier with Gene Tierney & Rex Harrison. In the TV version, Hope Lange & Edward Mulhare were cast in the leads, but most people might remember the show for one of its supporting players.
Charles Nelson Reilly became a television fixture thanks to Ghost, playing Claymore Gregg, a relative of the late Captain Daniel Gregg (Mulhare). Claymore was a weasel in every sense of the word, but he was a bumbling weasel, whose failings and pratfalls were worth watching. ABC suits must've liked what they saw, because Reilly moved on to a Saturday morning fantasy-com, Lidsville, after Ghost ended, before achieving iconic status when CBS revived Match Game in 1973.
Claymore is front and center in this 2nd season episode, with Joe Flynn (ex-McHale's Navy) guest-starring as a personification of the Devil himself.
Hope Lange moved on to co-star with Dick Van Dyke in his 1971 sitcom, but Edward Mulhare, after a decade of spot guest appearances, would return in a more active role in 1982's Knight Rider, which I think most people might associate him with today.