Seems to be heavily in use for Claudia, Queen of the Seventh Grade. Claudia is demoted to seventh grade, and her new classmates elect her their queen - seriously, this is an actual titled position, and is apparently a Stoneybrook Middle School tradition. Setting aside the fact that it was never mentioned in the earliest books in the series, when the club members were all in seventh grade, it's hard to understand how the school officials would be okay with giving the title to someone who is repeating the year. Many schools would consider this as unfair to the students who are going through that grade for the first time.
Richard Spier's overprotectiveness and high/age-inappropriate standards for Mary Anne's behavior become a lot more understandable after the revelations of Mary Anne and the Secret in the Attic. Not only did he lose his beloved young wife to cancer, but her parents threatened to sue him for custody of their granddaughter if he were deemed "unfit" as a parent. No wonder he went overboard in raising a sweet, demure young woman who's too meek for her own good.
Claudia's grandmother Mimi could be considered to have a Meaningful Name in her native language, Japanese. "Mimi" in Japanese means "ear", and especially in the beginning of the series, Mimi was the family member who Claudia could count on to listen to her and be understanding of her problems.