Kill your Sim. There are a lot of ways to do this, but starting a fire is the fastest. Once your Sim is dead switch, to direct control (if not already in it). As a dead Sim you can walk through walls and talk to Sims. Terrorize, Wail, and Possess are social options dead Sims can do. Unfortunately you cannot actually possesses Sims out of social mode. These social options have no effect on other Sims, but are funny. You can also challenge the Grim Reaper in fiddle challenge. You have an unlimited number of chances to try this. If you win, your Sim will become alive again. You can also pay the Grim Reaper 100 Simoleons for a Back To Life Ticket.