Not A Single Story But Several

Poul Anderson's The Merman's Children, like the same author's The Star Fox, turns out to be a series or serial rather than a single continuous narrative. Each "Book" is an installment describing an encounter with a different kind of supernatural being. Two parts of the book had previously been published elsewhere.

I read somewhere that Arthur Conan Doyle consciously invented the series as opposed to the serial because of the periodical publication of prose fiction. A series is a new kind of serial in which each episode is a complete story so that the reader does not have to remember the previous episode and does not have to wait for the next episode but might nevertheless recognize and appreciate the continuity of the characters and their setting, whether it is Victorian London or the bridge of the Enterprise.

Recently, TV adaptations from another medium have transformed several supporting characters into more substantial dramatis personae:

Chloe Sullivan introduces Clark Kent to James Olsen;
Lionel Luthor confronts and threatens Oliver Queen;
Lana Lang tries to kill Lex Luthor because Lex is possessed by Zod;
several of these individuals share Thanksgiving Dinner at the Kent farm.

Discussion of Smallville really belongs on Comics Appreciation but I am on a roll with Poul Anderson Appreciation and also want to make the point that we appreciate series with their continuing characters in many media and genres.