I have just done a major F Up, I was not even thinking when doing it. I have a well known mod that makes sims not part of the household selectable. I had Santa arrive to the lot in game (via cooking cookies) and basically Santa seemed to be obsessed with my household toilet so without thinking, I made him selectable so I could cancel the action of him using my toilet and then made him unselectable instantly.

I know that doing this could corrupt a neighbourhood, but I didn’t do anything with him such as getting him married, impregnating another sim or even interacting with anyone other than to cancel that 1 action because it was driving me crazy.

Is my game now going to start messing up? I feel like an idiot for doing this, but that mod has become so second nature to me via my gameplay that I didn’t even consider what I was doing.

Santa is known to not be able to hold his bladder. All those cookies and milk add up! XD

I personally wouldn't think that you did anything game corruptible by just kicking him out of the loo, but you could check your objects.package for a recent save.

Making him selectable does not edit the objects.package. Actually adding him to the family is harmful. Just to be safe, check the objects.package of your most recent EP or SP. If it was modified after you installed the game, it is corrupted. I doubt that will happen though.

Not only does making sims selectable not edit objects.package, but you can always just make objects.package and other game files read-only and then no matter what you do in the game it won't be edited. (Santa is not in objects.package, by the way, he's in the Happy Holidays files which should probably also be marked read-only because they contain him and a couple other NPCs from that pack).

Just run the hoodchecker in case he left some bits behind.

I would not worry too much.

I think the Happy Holidays pack has 3 NPCs, Santa, Father Time and Toddler New Year.
The file that should be made read only in the Happy Holidays Pack exist in the BG files as it was bundled with the game in most versions. I think it's H05.package.

All of the sims files in Program Files can be made read only, right? It's just the ones in My Documents that need to change?

Yes.

Some extra text so that MTS lets me post this

Yup, the same as Kestrellyn. The my documents directory has userdata; the game needs to write there. Every time you do as little as place a neighbourhood decoration, the game saves it. If the files are read only it wont be able to save.

I hate that LOL. No succinct answers allowed!