Are these generic sims based on someone or on some past characters?

Thanks for all the explanations folks. It was lightly driving me nuts that these characters kept showing up for me in CAS. Started wondering if I had some issue with the random generator, but then I noticed they were all over the branding. Now it makes sense and I may go pull some of them out of the library and drop them into my save for fun now that I know they have stories to be told. :)