* FairForItsDay - Kindness towards the disabled was a theme in some of the books, putting them a little ahead of their time. Also, one of the boys learns the hard way that girls aren't all the gender stereotype he'd assumed they were (in this case, easily grossed out and frightened of bugs).
* ValuesDissonance - The treatment of girls and some racist elements show the time the books were written. This could be one reason a tomboyish girl was added in the movies. One "of-the-times" example of this is [[https://static.tvtropes.org/pmwiki/pub/images/sugar_creek_gang_-_stupid_sexism_3133.jpg here]].