Hello!, I had just installed a lot of expansion packs when I first noticed the problem. In Appaloosa plains, a sim's home had a weird name with "/" and ":", I overlooked this problem and carried on playing the game. It later resurfaced as just yesterday I installed Roaring Heigths and now all the community lots as well as sims have names like : DOT11_World/Occupied/LotName:OccupiedSimsHouse06 or DOT11_World/Household:Nest!!!
As you might imagine, this has been a really frustrating problem, I'm not a freak but if the names of sims, lots and lot types (which are usually humorous and entertaining) are all wrong, I can't play the game. Please I would appreciate any help with this problem, I just need it to be fixed.

+Please don't make me uninstall and reinstall the games and EPs

-- > I've uninstalled the world ( deleted every file related to it), I will try installing it again

You only need to uninstall and reinstall the pack where the world is messed up, not everything.

Oh hey Emma! I was on your site some days ago. I will try installing it a second time, but if it still has the same problem, I'll just forget about it. But what do you mean by pack?

*Looks behind shoulder. No Emma. It's eLLa, dear.

The pack refers to whichever Expansion Pack or Stuff Pack where you get the funny strings instead of names. If issue is clearly isolated by the world(s) that come with EPs or on the Catalog thumbnails just for those respective pack(s), if they are the only ones affected. And none of the base game items are similarly affected. So, in your case, you may only need to uninstall and reinstall the Pets EP.
Sadly, uninstalling and reinstalling is the only way I know to correct this, as the cause is a corrupt .package which contains the STBL strings and names. Unless, the last install is also accompanied by a patching process. Then it could also be caused by patching (updating of the files).
Incidentally, what patch version is the base game running?

My base game is 1.67.2.024002 but I don't know if the game's patch was that or different... Anyways I've solved the problem by reinstalling, Thank you Ella! (And keep up with your good work!)