Bewitched - Season 8 - Eps 3: Samantha and the Loch Ness Monster
Sam and Darrin visit Inverness, Scotland, the place famous for the Loch Ness and its legendary monster. It seems that the monster is actually a warlock named Bruce who was transformed by Serena. To save Bruce's life, Sam calls on Serena to get him out of the spell. Once transformed, Bruce decides to get even with Serena by giving her a mermaid's tail! The reporters go crazy about the Loch Ness Monster, and Bruce wants to be a monster again. So he changes Serena back and Serena returns the favor by sending him back to the way he used to be, but with a little understanding about how important he really is.
About Bewitched

Title: Bewitched
First Air Date: 1964-09-17
Last Air Date: 1972-03-25
Status: Ended
Rating: 7.861/10 (from 695 votes)
Language: EN
Seasons: 8
Total Episodes: 254
Network: ABC
Genres: Sci-Fi & Fantasy, Comedy, Family, Drama
Production Companies: Columbia Pictures Television, Screen Gems
Synopsis
Samantha Stephens is a seemingly normal suburban housewife who also happens to be a genuine witch, with all the requisite magical powers. Her husband Darrin insists that Samantha keep her witchcraft under wraps, but situations invariably require her to indulge her powers while keeping her bothersome mother Endora at bay.
Cast

Elizabeth Montgomery
Samantha Stephens

Dick Sargent
Darrin Stephens

Agnes Moorehead
Endora

David White
Larry Tate