I think it would be really cool if there was an easter egg wherein, you name a character after a book character, and, if they look similar enough, someone like the book character's fictional spouse, with the same name, will ask to marry them. Then they will have the kids that the characters had. After they've had all the kids that the characters had, they'll start having random kids, as usual. I know that there would be copyright issues, but JK Rowling at least (I've heard) will let you get away with anything, as long as she likes it. She'd probably think that a Harry Potter Virtual Family was hysterical!

Some suggestions for books that would totally be worth doing...
Harry Potter
Star Wars
The Hunger Games
Yeah, stuff that's popular.

Another idea, in Virtual Villagers, you can set the speed for different things, which you couldn't do in VF (not so sure about VF2). Maybe you could speed up special events, like emails and chance cards?

Maybe it could also be less of a chance to adopt people? Maybe there could be a little tab for adopting kids for your family?