List of Sims 2 Very Bad Things

On Mod The Sims and More Awesome Than You, there are lists of things NOT to do when playing Sims 2. Some of these Very Bad Things will simply corrupt one neighbourhood. Others will corrupt the installation.

First, the neighbourhood corrupters:

• Deleting sims from the Family Bin
• Deleting sims doesn't completely delete them from the game and other sims will have memories of sims that no longer exist, and there will be orphaned(or unlinked) wants and fears files
• Moving inhabited lots to the Lots and Houses Bin, and moving those lots to another Neighbourhood
• Does almost the same thing as deleting sims from the neighbourhood via the Family Bin
• Moving the household to a new neighbourhood will cause the game to create copies of sims they have memories of meeting
• Saving while a sim is on the phone and then installing a new Expansion Pack or Stuff Pack
• Creates offworld loiterers if the lot is reset by installation of a new EP/SP
• Can also happen when installing some mods
• To remedy this, use the Lot Debugger from More Awesome Than You and select 'Nuke...' -> 'Offworld Loiterers'
• Deleting custom foods without deleting memories of eating them using SimPE
• Corrupts want trees
• Letting the initial pregnancies of Samantha Ottomas or Sarah Crittur come to term in an unpatched game
• The pregnancies of the pre-made pregnant Family Bin sims can have corrupt father data, and the fathers of the babies could be any random sim residing in that neighbourhood, or even another neighbourhood
• The patch only works if it is applied before the Family Bin sims are created with the Weather or Pets stealth neighbourhoods
• Making certain NPCs playable(they have incomplete or no character data):
• Social Worker
• Repo Man
• Carpool/taxi drivers
• Unsavory Charlatan(may cause game corruption as well, so don't do it!)
• Wise Man
• Witch Doctor
• Certain dead pre-made sims like Lyla Grunt, most of the other dead sims in  Olive Specter's graveyard
• Deleting tombstonse or urns(unless you have nounlinkondelete from More Awesome Than You)

Now for the Game Corruptors:

• Deleting any textures or other objects that came with the base game or EPs/SPs
• Making Universal NPCs playable:
• Grim Reaper
• Hula Zombies(hula dancers that appear with the Grim Reaper when a sim dies of old age in gold or above aspiration)
• Mrs. Crumplebottom
• Bigfoot Bigfoot(he's a template for the playable Bigfoots)
• Therapist(the funny doctor that appears whenever a sim goes into aspiration failure)
• Santa Claus(he visits a sim's house when a tree and santa cookies are present)
• Robot NPCs(they make the rover and hover bots move)
• Remote control toy NPCs(they make the RC cars and other remote control toys move)
• Stinky Skunk(again, a universal NPC)
• Father Time(and Toddler New Year) - they only appear on the lot during a New Years Bash party
• Tour guides
• Local chefs(from Vacation food stands)
• Ideal Plantsim
• Pollination Technician(he knocks the males up when they get abducted)
• Letting a vampire bite any of the Universal NPCs
• Turning any of the Universal NPCs into different creatures, including zombies, witches, plantsims or werewolves
• This changes their character files and I don't completely understand what happens, but doing this to them might create a different instance so the next time they are called to appear, it causes an error.
• Killing the Universal NPCs

There is a glitch in Nightlife where once a Grand Vampire bites a sim, the vamp will then bite any other townies or NPCs that he or she knows, including the Universal NPCs. There is a mod at More Awesome Than You, creaturefixes, that curbs the random biting.

Another step to take at preventing accidental game corruption is to find the objects.package file in the folder for your current expansion pack. It's usually C:\Program Files\EA GAMES\[Current EP]\Res\Objects

Right-click on the Objects.package file, then select 'Properties'. Once the Properties window opens, go down to the 'Attributes' section of the first tab and check the box to the left of 'Read Only'. Press 'Apply' and then 'Close'. Your Objects file is now protected. That doesn't mean you should then feel free to experiment with the Universal NPCs all you want, but rather it is just a protection in case something happens to one of them by accident. You can never be too careful when playing Sims 2, because it is quite buggy.