Life state
Each expansion pack for "The Sims 2" released to date has added an alternate state in which Sims can exist. These states have unique triggering techniques, advantages and disadvantages. These states are:
Servos: Released with Open For Business. Sims can build robots on the robot creation bench which becomes a member of the sims family. If they have a gold talent badge in robot making that is. A servo has different needs to a normal sim. Begin a robot they don't need to eat or sleep, however they do need power, which can be attained by sleeping or 'recharging' in the sunlight. Should a servo's power go into red, the servo will 'go beserk' and need to be fixed by a sim with a high mechanical skill.
Werewolves: Released with Pets. Occurs when sim is bitten by leader of the pack. The leader has yellow glowing eyes and comesto your lot at night. Werewolves are sim by day and wolf by night. Being a werewolf also slowly alters statistics such as skill points (body) and personality (playfullness). It also lets you train dogs faster.
PlantSims: Released with Seasons