So. If you type in "boolProp testingCheatsEnabled true", and shift-click on a mailbox and select "Make Me Know Everyone", the selected Sim will instantly know every single Sim there is in the game. Even all the Sims from another neighborhood.

To clear the situation:

When you start the game, there are two neighborhoods: Pleasantview and Veronaville.

You open the Dreamer family (Pleasantview), and you make Darren know everyone.

Darren now knows Regan Capp (and of course, the rest of Capps, all Montys, all Summerdreams, all Veronaville NPCs).

Darren makes a move with Regan.

The player makes a mistake in Veronaville, for example deleting an entire graveyard, marrying a Social Worker, or just decides to recycle the neighborhood.

So therefore, the player deletes Veronaville.

The player loads the Dreamer family. \OR/ The player is on a community lot, playing Daniel Pleasant. Suddenly, a wild Darren appears!

Does the player destroy Pleasantview?

It strikes me that if this cheat works as described, Pleasantview and Veronaville would both be broken from the moment it happened and it was time to restore from backup or reset all your neighborhoods as soon as you did it.

DJ., if your neighborhood is corrupted and before you delete the neighborhood or go back to a back up, can you test something for me?

Can you call someone from another neighborhood and see if they can be invited over? Can you see if they will actually show up?

Imagine if you are like me and only play neighborhoods a couple months and have like 8+ neighborhoods! Glad I never used that.

They're completely different sets of files so no.

Wait, why would that command actually work between neighborhoods? That's a rather strange behavior, and why is that ability even in the game? (Seeing as there's no inter-neighborhood relationships except the Occupied Lot Sim Bin).

Oh well, but then how is it possible that they could know everyone and not beb able to contact them? Since, as you said:

I think the important thing to determine here is IF that cheat works as DJ describes. It's hard to imagine how it could, but I'm not a programmer. If it could, then whatever wildly improbable bit of coding allows that could conceivably be used to call a sim from another hood. Scattering more bits of code shrapnel as it went.

But I'm not about to use it in my game to find out!

It only makes you know all the Sims in a neighborhood, not the entire game. I used it a long time ago, before I knew it was a very bad thing to do.

That is not how the cheat works. The only way to get the behavior that the OP documents is to have Pleasantview and / or Veronaville as subhoods in the same neighborhood.

We know this because the Sim Relations records (SREL) are keyed on the Sim Description instance number, which only exists in the current neighborhood.

The cheat does nothing fundamentally wrong, but will slow down your game because it takes a while to bring up such a full relationship panel in the game.

[Update:] ... and just to be sure, I tried it in-game. Sure enough, the behavior documented by the OP does not occur.

I used that cheat a long time ago when I first started playing (before I knew it was a VBT). Nothing bad ever happened to my knowledge, but I never used it again. (Especially now that we have Phaenoh's phone book to look up people my sims don't know.)

Because they're completely different sets of files so no - see Moo.

Yeah, I know, I did, apparently that wasn't how the cheat worked.

Considering the last time I used the cheat is with only base game, probably like 6 years ago or something. But it's just so clear in my head, that you could invite someone from another neighborhood...

But thank you for clearing that for me and everyone else, Mootilda. I was planning to use the cheat on a Sim I was about to recycle, so I could resurrect the Tricous. Heh. But then I started thinking.