Well, I found this thread, and I can’t resist. More than you ever wanted to know about Sweet Valley, or at least about the Twins series…
Jessica’s club was the Unicorn Club. It is mentioned in nearly all the books, sometimes as an important focus, sometimes more as an aside. The club, in two somewhat different incarnations, also formed the basis of a spinoff series of the Twins, aptly named the Unicorn Club series, in which the girls and their friends were in seventh grade.
The last book in the Twins series served as a kind of bookend to the whole set. The girls were sixth graders throughout the series till this book. In the last one, they were about to enter eighth grade. The book included a few characters not introduced in the Twins series but present in the Unicorn Club books–most notably Rachel Grant, a wealthy African American counterpart to Lila. The book served as a leadin to a new and not very successful series about the kids attending a new junior high school.
The gossip was named Caroline Pearce.
The details of how Mr. and Mrs. Wakefield met varied from book to book and series to series. Besides the two stories mentioned above, there was also one Twins book in which they described how they met at college (more specifically, at Sweet Valley University before it was called that, and even more specifically, while teammates in a pickup volleyball game). Some items have to remain consistent from one book to the next. But when you are producing a book every couple of months for each of four major series, many other things kind of go by the boards.
The fat girl was indeed Lois Waller. Robin was the name of the twins’ coolest cousin, who lived down San Diego way and made an occasional appearance. She was the daughter of Mrs. Wakefield’s favorite–but as it turns out not ONLY–sister.
There. The expert speaks.
[No, I am not Francine Pascal, though she does actually exist. But I WAS one of the ghostwriters for the series–now it can be told–and I wrote a bunch of Twins and Unicorn books from outlines. It was fun, though the deadlines were tight, and it helped keep my kids in Cheerios.]