The Sims 3: how to have ghosts in the house
Here's what to do to see some ghosts in your garden
Go to the cemetery, click on all the tombstones and take as many as possible. Come back to your house and put them somewhere in your backyard. You now have a 70% chance of seeing one or more ghosts wandering around the house every night. To improve the chances of success write in the epitaph "Here lies [Sim's name], the one who returns".