I my save game there is a version of Harry Potters parents and their friends walking around. They are all young adults and roommates. Obviously they are all spellcasters as well. I needed some friends for my first spellcaster sim and they seemed like a good idea. I edited a San mychuno apartment to suit a spell household. I don't know if they are totally accurate. they are mostly my interpretation of the book characters. I made zero effort for them to resemble the actors who portrayed them.
The other fictional household in my game is scoobidoo . I needed 'volunteers' to investigate in forgotten hollow and accidentally become vampires. It was a requirement for my supersim to turn others into vampires. There is some accuracy but I don't mind if they don't match the cartoon characters completely.
As my main sim however, I tend to stick to my own characters, not characters of a story.