If I use characters from TV, movies and books, it's because they fit the theme I'm playing with my main characters. So, I just set them down in the existing world in a living environment that's appropriate, then turn them over to the game. For example, in my current save, I have the Addams family waiting in the wings to be placed. I just haven't figured out if they are in The Myst or outside in the human world, so they aren't there yet. I won't play them when I place them, though. They will just live there and become part of the town.
I was once playing a '60's themed game in Sims 3. My main family was a group of surfer dude brothers. I populated Isla Paradiso with characters from 60's TV shows and pop culture. I had The Addams Family, Gilligan's Island, The Beatles (living in a yellow submarine), I Dream of Jeannie, The Beach Boys, and a bunch of others. I then turned them over to the game. It was hysterical to see Morticia Addams running a food stall at the summer festival. She got her revenge, though. I'm pretty sure the Addams Family with house I downloaded from the exchange contained the bad cc that caused the "stretched baby" glitch in that save.