Pic of the day: Marsha Bruenig as you have never seen her before.
At least in the NightLife expansion to The Sims 2, there is a command you can enter: AgeSimsCheat On. (To enter a command, press Ctrl+Shift+C. If it doesn't close automatically after the command, use Exit to leave command mode.) With this cheat on, you can change the age of any character, even a non player character.
This works excellently if all you need them for is background scenery. If you want Marsha and Orlando and the other kids to grow up together with your character and grow old together, you can use this to age them up one age at a time. You can also reduce old Sims to children, and pretend they are the great-grandchildren of the original or something. The game doesn't support this function all that well, though. Not when you get a little closer.
I used AgeSimsCheat On to make Marsha Bruenig into a teenager, and later sent her to the university together with one of my Sims. When you send townie teens to the uni, they become playable characters. Here I learned that she still has the children's "Grow Up" aspiration. Since she was now grown up, kinda, she displayed platinium mood all the time. But she wasn't actually in platinium mood, so took damage from using aspiration reward objects for instance. Pretty confusing. It is probably still safer to use the Tombstone of Life and Death to add her to a family and then move her forward to birthday, using "boolprop TestingCheatsEnabled True".
Another use for AgeSimsCheat was to change a senior citizen (Jordan Turner, from Downtown) to a child. This didn't quite work out either. She did not follow the children home from school, like other kids randomly did. Or perhaps she just didn't do it often enough to happen while I played. But she also kept her job downtown on one of the restaurants. It is kind of strange to see a kid stand there...
There is good reason to recycle non-player Sims instead of just killing them, though. If the neighborhood has too many person files (more than around 800 up to Uni, but supposedly thousands after NightLife), the game will get eaten by bugs and become unplayable. Or in the more colorful language of J M Pascedo, it will blow up in a fireball visible from space. This is bad game design and not easy to fix, though it helps greatly to not move Sims from one neighborhood to another. (There are also a few downloads from More Awesome Than You which attempt to fix a couple of the bugs.) Dead NPCs still count toward the quota, so killing them and making new ones is not a good solution! There is a secret command to nuke all NPCs to oblivion and create new ones from scratch, but this seems like overkill and will probably not clear out the deceased ones anyway.
Presumably if enough townies die, new ones will be generated to replace them. I really don't know that from experience, as I have never made such an inroad in the native population. I do know that NPCs like the cow mascot will be replaced almost immediately if she marries into a family, but on the other hand it seems that no new children are generated if you elevate some of the existing to teens. Likewise even if you send a couple townie teens to college, they won't be replaced right away. Perhaps there is a minimum level that sets of the townie generator. If I see it, I will definitely want to tell you.
But for now, the only way townies disappear in my neighborhood is if they marry into a family, grow old and die... or if they are evil enough to be fed to the cow plant. (Komei Tellerman is cow fodder on sight, for instance, but I'm sure you all guessed that if you've played this game.)
Visit the archive page for the older diaries I've put out to pasture.